Have you ever wondered whether to write checkup or check up? Both spellings are commonly used in English, especially when talking about a medical examination.
However, the spelling you choose can depend on the style guide, dictionary, or publication you follow.
Understanding how these forms work will help you write more clearly and confidently.
The word usually refers to a routine medical examination that helps a doctor assess someone’s health.
For example, you might schedule a yearly checkup, take your child for a check-up, or visit a dentist for a regular examination.
Although the two spellings generally have the same meaning, one word checkup is widely accepted, particularly in American English, while hyphenated check up is also correct in many contexts and is especially familiar in British English.
In this guide, you will learn the difference between the two forms, see practical examples, and discover which spelling to use in everyday writing, schoolwork, and professional communication.
Quick Answer
Checkup and check-up are both correct spellings of the noun meaning a routine examination, especially a medical examination. Checkup is common in American English, while check-up is often seen in British English. Choose one spelling and use it consistently throughout your writing. The verb form is written as two words: check up.
Why Do People Confuse Checkup and Check-Up?
People often confuse checkup and check-up because they look almost identical and usually express the same idea. The only visible difference is the hyphen.
English uses several spelling patterns for compound words. Some compounds are written as one word, some use a hyphen, and others remain separate words. Over time, a compound may develop more than one accepted spelling.
For example:
- Checkup: She has a checkup next week.
- Check-up: She has a check-up next week.
- Check up: The nurse will check up on the patient tomorrow.
The first two examples use nouns. The third uses a verb phrase followed by the word on.
The confusion often arises because learners assume that one spelling must be correct and the other must be wrong. In this case, both noun spellings are acceptable, although regional preferences and editorial styles may differ.
First Word: Checkup
Checkup is a noun that means an examination or assessment, particularly one performed to evaluate a person’s health.
It is widely used in American English and appears in everyday writing, medical information, and general communication.
Meaning of Checkup
A checkup is usually a planned examination rather than a visit prompted by an emergency. A doctor may check your blood pressure, ask about symptoms, review your medical history, or recommend tests during a checkup.
The word can also be used more broadly for an inspection or review of something.
Examples of Checkup in Sentences
- I have a dental checkup on Friday.
- The doctor recommended a yearly checkup.
- My son needs a routine checkup before school starts.
- She went to the clinic for a general health checkup.
- The mechanic performed a checkup on the car.
In the last example, checkup refers to an inspection rather than a medical examination.
Is Checkup One Word?
Yes. Checkup is correctly written as one word when used as a noun. It is particularly common in American English.
For example:
- Correct: I scheduled a checkup.
- Correct: He needs a routine checkup.
- Incorrect in standard usage: I scheduled a check up.
In the final example, the intended meaning is a noun, so the one-word spelling or the hyphenated spelling is preferable.
Second Word: Check-Up
Check-up is a noun with the same basic meaning as checkup. It refers to an examination, inspection, or assessment, especially a routine medical appointment.
The hyphenated form is widely recognized and is often used in British English. It also appears in other varieties of English and in publications that prefer hyphenated compounds.
Meaning of Check-Up
A check-up is an opportunity to assess whether someone or something is in good condition.
For example, a medical check-up may help identify health concerns, while a car check-up may reveal a maintenance problem.
Examples of Check-Up in Sentences
- I am going to the hospital for a check-up.
- The dentist advised me to have a regular check-up.
- She booked a check-up for her elderly father.
- The doctor said that my check-up went well.
- The car needs a check-up before our long journey.
Is Check-Up One Word or Two?
Check-up is written as one compound noun with a hyphen. It is not the same grammatical form as the verb phrase check up.
Compare these sentences:
- Noun: I need a check-up.
- Verb phrase: I need to check up on my friend.
In the first sentence, check-up names an examination. In the second, check up on means to find out how someone is doing.
Checkup vs Check-Up: Comparison Table
| Feature | Checkup | Check-Up |
|---|---|---|
| Part of speech | Noun | Noun |
| Main meaning | An examination or assessment | An examination or assessment |
| Spelling | One word | One word with a hyphen |
| Regional preference | Common in American English | Often seen in British English |
| Medical example | I booked a checkup. | I booked a check-up. |
| Meaning difference | Generally none | Generally none |
| Best approach | Follow your chosen style guide | Follow your chosen style guide |
The key point: Both forms can be correct as nouns. The difference is mainly spelling preference, not meaning.
When Should You Use Checkup or Check-Up?
Choosing between checkup and check-up is usually straightforward once you consider your audience and writing style.
1. Use Checkup in American English
If you are writing for an American audience, checkup is a natural and widely accepted choice.
Examples:
- I have my annual checkup tomorrow.
- The pediatrician scheduled a checkup for the baby.
- Regular checkups can help monitor your health.
2. Use Check-Up in British English When Appropriate
If your audience follows British English conventions or your preferred dictionary uses the hyphenated spelling, check-up is a suitable choice.
Examples:
- I have a medical check-up next week.
- She went for her annual check-up.
- The doctor recommended a routine check-up.
British English also uses checkup in some contexts, so the hyphenated version is a preference rather than an absolute rule for every British writer.
3. Follow Your Style Guide
If you are writing an academic assignment, report, article, or business document, check the relevant style guide or dictionary.
For example, a publication may consistently use checkup, while another may prefer check-up. Either way, consistency matters more than switching between forms without a reason.
4. Use Check Up for the Verb Phrase
When you mean to investigate, monitor, or find out how someone or something is doing, use the two-word verb phrase check up.
Examples:
- I will check up on my grandmother tonight.
- The manager checks up on the team regularly.
- The nurse checked up on the patient after surgery.
Remember that the phrase often takes on when referring to monitoring a person or situation.
12 Examples of Checkup and Check-Up in Sentences
The following examples show how both noun spellings work in everyday English.
- Checkup: I need to schedule a checkup with my doctor.
- Check-Up: She booked a check-up for next Monday.
- Checkup: My annual checkup is usually in October.
- Check-Up: The dentist recommended a routine check-up.
- Checkup: The baby had a checkup after birth.
- Check-Up: He went for a medical check-up before traveling.
- Checkup: Regular checkups can help monitor your overall health.
- Check-Up: My father has a heart check-up every year.
- Checkup: The doctor completed my checkup in twenty minutes.
- Check-Up: She felt relieved after her check-up.
- Checkup: The mechanic gave the car a complete checkup.
- Check-Up: The school required a health check-up for the child.
Both forms work as nouns in these examples. The best choice depends on the spelling convention you are following.
Examples of Check Up as a Verb
These additional sentences illustrate the difference between the noun and the verb phrase.
- I will check up on my friend after her operation.
- The supervisor checks up on new employees during their first week.
- The doctor asked the nurse to check up on the patient later.
In these examples, check up describes an action, not an examination named by a noun.
Common Mistakes With Checkup and Check-Up
Even though these spellings are simple, writers sometimes use them incorrectly. Here are the most common mistakes to avoid.
Mistake 1: Assuming Check-Up Is Always Wrong
Incorrect assumption: Check-up is never correct because it contains a hyphen.
Correction: Both checkup and check-up are accepted noun forms. Follow the conventions of your audience or publication.
Mistake 2: Assuming Checkup Is Always Wrong in British English
Incorrect assumption: British English must always use check-up.
Correction: The hyphenated form is common in British English, but the one-word spelling also appears. Regional preferences do not create an absolute rule for every writer.
Mistake 3: Writing the Noun as Check Up
Incorrect: I have a check up tomorrow.
Preferred in standard edited writing: I have a checkup tomorrow.
Also correct: I have a check-up tomorrow.
When the intended meaning is a medical examination, use the one-word or hyphenated noun form.
Mistake 4: Confusing the Noun With the Verb Phrase
Incorrect: The doctor will checkup on me tomorrow.
Correct: The doctor will check up on me tomorrow.
Here, check up on is a verb phrase, so it is written as separate words.
Mistake 5: Switching Spellings Without a Reason
Less consistent: I booked a checkup, and my next check-up is in June.
Better: I booked a checkup, and my next checkup is in June.
The original sentence is understandable, but using one spelling throughout a document gives your writing a more consistent appearance.
Memory Trick: How to Remember Checkup vs Check-Up
Use this simple memory trick:
One examination, one noun: Write checkup or check-up when naming the examination.
An action, two words: Write check up when describing the act of checking on someone or something.
Remember these examples:
- Checkup: I need a checkup.
- Check-up: I need a check-up.
- Check up: I will check up on him.
You can also remember the difference by asking yourself a question: Is the word naming an examination, or is it describing an action?
If it names an examination, use checkup or check-up. If it describes an action, use check up.
American vs British English: Checkup or Check-Up?
American and British English sometimes differ in how they spell compound words. Checkup and check-up are a useful example of this variation.
American English
In American English, checkup is a common spelling.
Examples:
- I have a checkup with my doctor.
- My annual checkup is next month.
- The doctor recommended regular checkups.
British English
In British English, check-up is a familiar spelling, particularly in everyday references to medical examinations.
Examples:
- I have a check-up with my doctor.
- My annual check-up is next month.
- The doctor recommended regular check-ups.
Which Spelling Is Better?
Neither spelling is universally better. If you are writing for American readers, checkup is a practical choice. If you are writing for a British publication that prefers check-up, use that form.
The important thing is to follow your chosen spelling convention consistently.
Similar Words to Checkup and Check-Up
Understanding related terms can help you choose the most appropriate word for a particular situation.
| Word or Phrase | Meaning | Example |
|---|---|---|
| Examination | A formal inspection or assessment | The doctor performed an examination. |
| Medical checkup | A routine assessment of health | I have a medical checkup tomorrow. |
| Physical | A medical examination, often covering general health | She needs a physical before starting college. |
| Health screening | A test or set of tests for particular health conditions | The clinic offers a health screening. |
| Inspection | A careful examination of something | The mechanic carried out an inspection. |
| Check up on | To find out how someone or something is doing | I will check up on my neighbor. |
| Follow-up | A later appointment or action after an earlier event | The doctor scheduled a follow-up visit. |
| Check-in | An act of reporting, registering, or confirming arrival or status | The nurse completed the patient’s check-in. |
These terms are related, but they are not always interchangeable. For instance, a screening may focus on a specific condition, while a routine checkup may cover several aspects of a person’s health. A follow-up usually takes place after an earlier appointment, treatment, or assessment.
Final Verdict: Checkup or Check-Up?
Both checkup and check-up are correct as nouns. They generally mean the same thing: a routine examination, especially a medical examination.
Choose checkup for a straightforward American English style. Choose check-up when it matches your British English preference or your publication’s spelling guide.
Do not confuse either noun form with check up, the two-word verb phrase used in sentences such as “I will check up on my friend.”
If you remember only one thing, remember this: the noun can be written as one word or with a hyphen, but the verb phrase is written as two words.
Frequently Asked Questions
1. Is checkup one word or two?
Checkup is one word when used as a noun meaning an examination. The hyphenated form check-up is also accepted. The verb phrase check up is written as two words.
2. Is check-up grammatically correct?
Yes. Check-up is a correct noun spelling used for a routine examination, especially a medical examination. It is common in British English and is also understood in other varieties of English.
3. Is checkup or check-up correct in American English?
Checkup is a widely used spelling in American English. However, check-up is also recognized. For American writing, checkup is a sensible default unless your style guide specifies otherwise.
4. Is check-up British English?
Check-up is a familiar spelling in British English, but it is not exclusive to Britain. The one-word form checkup is also used. The best choice depends on the dictionary or style guide you follow.
5. Should I write annual checkup or annual check-up?
Both are acceptable. For example, “I have my annual checkup in May” and “I have my annual check-up in May” are both correct. Choose the form that matches your preferred spelling convention and use it consistently.
6. What is the difference between checkup and check up?
Checkup is a noun referring to an examination. Check up is a verb phrase describing an action, often used with on to mean monitoring someone or finding out how they are doing.
Examples:
- Noun: I need a checkup.
- Verb phrase: I will check up on my brother.
7. Is checkup hyphenated?
The spelling checkup is not hyphenated. The alternative form check-up contains a hyphen. Both can be correct as nouns, depending on the spelling convention being followed.
8. What is the plural of checkup?
The plural of checkup is checkups. The plural of check-up is check-ups.
Examples:
- The clinic offers annual checkups.
- The clinic offers annual check-ups.
Both plural forms are correct when they follow the spelling used for the singular noun.
Remember This
- Checkup: One-word noun, commonly used in American English.
- Check-up: Hyphenated noun, often seen in British English.
- Check up: Two-word verb phrase, often used with on.
- Meaning: Checkup and check-up generally mean the same thing.
- Consistency: Follow your preferred
Checkup or Check-Up: Which Spelling Is Correct?
Have you ever wondered whether to write checkup or check-up? Both spellings are commonly used in English, especially when talking about a medical examination. However, the spelling you choose can depend on the style guide, dictionary, or publication you follow. Understanding how these forms work will help you write more clearly and confidently.
The word usually refers to a routine medical examination that helps a doctor assess someone’s health. For example, you might schedule a yearly checkup, take your child for a check-up, or visit a dentist for a regular examination. Although the two spellings generally have the same meaning, one-word checkup is widely accepted, particularly in American English, while hyphenated check-up is also correct in many contexts and is especially familiar in British English. In this guide, you will learn the difference between the two forms, see practical examples, and discover which spelling to use in everyday writing, schoolwork, and professional communication.
Quick Answer
Checkup and check-up are both correct spellings of the noun meaning a routine examination, especially a medical examination. Checkup is common in American English, while check-up is often seen in British English. Choose one spelling and use it consistently throughout your writing. The verb form is written as two words: check up.
Why Do People Confuse Checkup and Check-Up?
People often confuse checkup and check-up because they look almost identical and usually express the same idea. The only visible difference is the hyphen.
English uses several spelling patterns for compound words. Some compounds are written as one word, some use a hyphen, and others remain separate words. Over time, a compound may develop more than one accepted spelling.
For example:
Checkup: She has a checkup next week.
Check-up: She has a check-up next week.
Check up: The nurse will check up on the patient tomorrow.
The first two examples use nouns. The third uses a verb phrase followed by the word on.
The confusion often arises because learners assume that one spelling must be correct and the other must be wrong. In this case, both noun spellings are acceptable, although regional preferences and editorial styles may differ.
First Word: Checkup
Checkup is a noun that means an examination or assessment, particularly one performed to evaluate a person’s health.
It is widely used in American English and appears in everyday writing, medical information, and general communication.
Meaning of Checkup
A checkup is usually a planned examination rather than a visit prompted by an emergency. A doctor may check your blood pressure, ask about symptoms, review your medical history, or recommend tests during a checkup.
The word can also be used more broadly for an inspection or review of something.
Examples of Checkup in Sentences
I have a dental checkup on Friday.
The doctor recommended a yearly checkup.
My son needs a routine checkup before school starts.
She went to the clinic for a general health checkup.
The mechanic performed a checkup on the car.
In the last example, checkup refers to an inspection rather than a medical examination.
Is Checkup One Word?
Yes. Checkup is correctly written as one word when used as a noun. It is particularly common in American English.
For example:
Correct: I scheduled a checkup.
Correct: He needs a routine checkup.
Incorrect in standard usage: I scheduled a check up.
In the final example, the intended meaning is a noun, so the one-word spelling or the hyphenated spelling is preferable.
Second Word: Check-Up
Check-up is a noun with the same basic meaning as checkup. It refers to an examination, inspection, or assessment, especially a routine medical appointment.
The hyphenated form is widely recognized and is often used in British English. It also appears in other varieties of English and in publications that prefer hyphenated compounds.
Meaning of Check-Up
A check-up is an opportunity to assess whether someone or something is in good condition.
For example, a medical check-up may help identify health concerns, while a car check-up may reveal a maintenance problem.
Examples of Check-Up in Sentences
I am going to the hospital for a check-up.
The dentist advised me to have a regular check-up.
She booked a check-up for her elderly father.
The doctor said that my check-up went well.
The car needs a check-up before our long journey.
Is Check-Up One Word or Two?
Check-up is written as one compound noun with a hyphen. It is not the same grammatical form as the verb phrase check up.
Compare these sentences:
Noun: I need a check-up.
Verb phrase: I need to check up on my friend.
In the first sentence, check-up names an examination. In the second, check up on means to find out how someone is doing.
Checkup vs Check-Up: Comparison Table
Feature
Checkup
Check-Up
Part of speech
Noun
Noun
Main meaning
An examination or assessment
An examination or assessment
Spelling
One word
One word with a hyphen
Regional preference
Common in American English
Often seen in British English
Medical example
I booked a checkup.
I booked a check-up.
Meaning difference
Generally none
Generally none
Best approach
Follow your chosen style guide
Follow your chosen style guide
The key point: Both forms can be correct as nouns. The difference is mainly spelling preference, not meaning.
When Should You Use Checkup or Check-Up?
Choosing between checkup and check-up is usually straightforward once you consider your audience and writing style.
1. Use Checkup in American English
If you are writing for an American audience, checkup is a natural and widely accepted choice.
Examples:
I have my annual checkup tomorrow.
The pediatrician scheduled a checkup for the baby.
Regular checkups can help monitor your health.
2. Use Check-Up in British English When Appropriate
If your audience follows British English conventions or your preferred dictionary uses the hyphenated spelling, check-up is a suitable choice.
Examples:
I have a medical check-up next week.
She went for her annual check-up.
The doctor recommended a routine check-up.
British English also uses checkup in some contexts, so the hyphenated version is a preference rather than an absolute rule for every British writer.
3. Follow Your Style Guide
If you are writing an academic assignment, report, article, or business document, check the relevant style guide or dictionary.
For example, a publication may consistently use checkup, while another may prefer check-up. Either way, consistency matters more than switching between forms without a reason.
4. Use Check Up for the Verb Phrase
When you mean to investigate, monitor, or find out how someone or something is doing, use the two-word verb phrase check up.
Examples:
I will check up on my grandmother tonight.
The manager checks up on the team regularly.
The nurse checked up on the patient after surgery.
Remember that the phrase often takes on when referring to monitoring a person or situation.
12 Examples of Checkup and Check-Up in Sentences
The following examples show how both noun spellings work in everyday English.
Checkup: I need to schedule a checkup with my doctor.
Check-Up: She booked a check-up for next Monday.
Checkup: My annual checkup is usually in October.
Check-Up: The dentist recommended a routine check-up.
Checkup: The baby had a checkup after birth.
Check-Up: He went for a medical check-up before traveling.
Checkup: Regular checkups can help monitor your overall health.
Check-Up: My father has a heart check-up every year.
Checkup: The doctor completed my checkup in twenty minutes.
Check-Up: She felt relieved after her check-up.
Checkup: The mechanic gave the car a complete checkup.
Check-Up: The school required a health check-up for the child.
Both forms work as nouns in these examples. The best choice depends on the spelling convention you are following.
Examples of Check Up as a Verb
These additional sentences illustrate the difference between the noun and the verb phrase.
I will check up on my friend after her operation.
The supervisor checks up on new employees during their first week.
The doctor asked the nurse to check up on the patient later.
In these examples, check up describes an action, not an examination named by a noun.
Common Mistakes With Checkup and Check-Up
Even though these spellings are simple, writers sometimes use them incorrectly. Here are the most common mistakes to avoid.
Mistake 1: Assuming Check-Up Is Always Wrong
Incorrect assumption: Check-up is never correct because it contains a hyphen.
Correction: Both checkup and check-up are accepted noun forms. Follow the conventions of your audience or publication.
Mistake 2: Assuming Checkup Is Always Wrong in British English
Incorrect assumption: British English must always use check-up.
Correction: The hyphenated form is common in British English, but the one-word spelling also appears. Regional preferences do not create an absolute rule for every writer.
Mistake 3: Writing the Noun as Check Up
Incorrect: I have a check up tomorrow.
Preferred in standard edited writing: I have a checkup tomorrow.
Also correct: I have a check-up tomorrow.
When the intended meaning is a medical examination, use the one-word or hyphenated noun form.
Mistake 4: Confusing the Noun With the Verb Phrase
Incorrect: The doctor will checkup on me tomorrow.
Correct: The doctor will check up on me tomorrow.
Here, check up on is a verb phrase, so it is written as separate words.
Mistake 5: Switching Spellings Without a Reason
Less consistent: I booked a checkup, and my next check-up is in June.
Better: I booked a checkup, and my next checkup is in June.
The original sentence is understandable, but using one spelling throughout a document gives your writing a more consistent appearance.
Memory Trick: How to Remember Checkup vs Check-Up
Use this simple memory trick:
One examination, one noun: Write checkup or check-up when naming the examination.
An action, two words: Write check up when describing the act of checking on someone or something.
Remember these examples:
Checkup: I need a checkup.
Check-up: I need a check-up.
Check up: I will check up on him.
You can also remember the difference by asking yourself a question: Is the word naming an examination, or is it describing an action?
If it names an examination, use checkup or check-up. If it describes an action, use check up.
American vs British English: Checkup or Check-Up?
American and British English sometimes differ in how they spell compound words. Checkup and check-up are a useful example of this variation.
American English
In American English, checkup is a common spelling.
Examples:
I have a checkup with my doctor.
My annual checkup is next month.
The doctor recommended regular checkups.
British English
In British English, check-up is a familiar spelling, particularly in everyday references to medical examinations.
Examples:
I have a check-up with my doctor.
My annual check-up is next month.
The doctor recommended regular check-ups.
Which Spelling Is Better?
Neither spelling is universally better. If you are writing for American readers, checkup is a practical choice. If you are writing for a British publication that prefers check-up, use that form.
The important thing is to follow your chosen spelling convention consistently.
Similar Words to Checkup and Check-Up
Understanding related terms can help you choose the most appropriate word for a particular situation.
Word or Phrase
Meaning
Example
Examination
A formal inspection or assessment
The doctor performed an examination.
Medical checkup
A routine assessment of health
I have a medical checkup tomorrow.
Physical
A medical examination, often covering general health
She needs a physical before starting college.
Health screening
A test or set of tests for particular health conditions
The clinic offers a health screening.
Inspection
A careful examination of something
The mechanic carried out an inspection.
Check up on
To find out how someone or something is doing
I will check up on my neighbor.
Follow-up
A later appointment or action after an earlier event
The doctor scheduled a follow-up visit.
Check-in
An act of reporting, registering, or confirming arrival or status
The nurse completed the patient’s check-in.
These terms are related, but they are not always interchangeable. For instance, a screening may focus on a specific condition, while a routine checkup may cover several aspects of a person’s health. A follow-up usually takes place after an earlier appointment, treatment, or assessment.
Final Verdict: Checkup or Check-Up?
Both checkup and check-up are correct as nouns. They generally mean the same thing: a routine examination, especially a medical examination.
Choose checkup for a straightforward American English style. Choose check-up when it matches your British English preference or your publication’s spelling guide.
Do not confuse either noun form with check up, the two-word verb phrase used in sentences such as “I will check up on my friend.”
If you remember only one thing, remember this: the noun can be written as one word or with a hyphen, but the verb phrase is written as two words.
Frequently Asked Questions
1. Is checkup one word or two?
Checkup is one word when used as a noun meaning an examination. The hyphenated form check-up is also accepted. The verb phrase check up is written as two words.
2. Is check-up grammatically correct?
Yes. Check-up is a correct noun spelling used for a routine examination, especially a medical examination. It is common in British English and is also understood in other varieties of English.
3. Is checkup or check-up correct in American English?
Checkup is a widely used spelling in American English. However, check-up is also recognized. For American writing, checkup is a sensible default unless your style guide specifies otherwise.
4. Is check-up British English?
Check-up is a familiar spelling in British English, but it is not exclusive to Britain. The one-word form checkup is also used. The best choice depends on the dictionary or style guide you follow.
5. Should I write annual checkup or annual check-up?
Both are acceptable. For example, “I have my annual checkup in May” and “I have my annual check-up in May” are both correct. Choose the form that matches your preferred spelling convention and use it consistently.
6. What is the difference between checkup and check up?
Checkup is a noun referring to an examination. Check up is a verb phrase describing an action, often used with on to mean monitoring someone or finding out how they are doing.
Examples:
Noun: I need a checkup.
Verb phrase: I will check up on my brother.
7. Is checkup hyphenated?
The spelling checkup is not hyphenated. The alternative form check-up contains a hyphen. Both can be correct as nouns, depending on the spelling convention being followed.
8. What is the plural of checkup?
The plural of checkup is checkups. The plural of check-up is check-ups.
Examples:
The clinic offers annual checkups.
The clinic offers annual check-ups.
Both plural forms are correct when they follow the spelling used for the singular noun.
Remember This
Checkup: One-word noun, commonly used in American English.
Check-up: Hyphenated noun, often seen in British English.
Check up: Two-word verb phrase, often used with on.
Meaning: Checkup and check-up generally mean the same thing.
Consistency: Follow your preferred dictionary or style guide throughout your writing.
Conclusion
The choice between checkup and check-up is simpler than it first appears. Both are accepted noun spellings for a routine examination, especially one related to health. The one-word form is common in American English, while the hyphenated form is familiar in British English. Neither should automatically be treated as incorrect.
To write clearly, consider your audience, follow the relevant spelling convention, and keep your usage consistent. Most importantly, distinguish these noun forms from check up, the two-word verb phrase. Once you understand that difference, you can confidently use checkup, check-up, and check up in everyday conversations, school assignments, and professional writing.
