How soon can you take a pregnancy test?
Most pregnancy tests are reliable from the first day of a missed period, or at least 21 days after unprotected sex if you do not know when your period is due.
Updated: 2026-10-05 • Published: 2026-10-04 • 4 sources cited
If you have missed a period and recently had unprotected sex, you may be pregnant. The NHS says pregnancy tests are most reliable from the first day of your missed period, which is why timing matters more than the brand of test or the time of day.
Waiting can be the hardest part. Some very sensitive pregnancy tests can be used even before a missed period, but a test taken too early is one of the main reasons a negative result may not be reliable.
This guide explains when a test is most reliable, how tests work, what can affect the result and where to get a test. If you are unsure what a result means for you, a GP, pharmacist or sexual health clinic can help.
When can you take a pregnancy test?
You can carry out most pregnancy tests from the first day of a missed period. The NHS describes this as the point from which tests are most reliable.
If you do not know when your next period is due, the NHS advice is to do the test at least 21 days after you last had unprotected sex. This gives a clear waiting time for people whose cycles are irregular or who are not tracking their periods.
Some very sensitive pregnancy tests can be used even before you miss a period. You can do a pregnancy test on a sample of urine collected at any time of the day. It does not have to be in the morning.
How does a pregnancy test work?
All pregnancy tests detect the hormone human chorionic gonadotrophin, usually shortened to hCG. The NHS says this hormone starts to be produced around 6 days after fertilisation.
Most pregnancy tests come in a box that contains 1 or 2 long sticks. You pee on the stick and the result appears on the stick after a few minutes.
All tests are slightly different, so always check the instructions that come with the test you are using. Following them correctly is one of the things that makes a home test accurate.
How accurate are home pregnancy tests?
Home pregnancy tests are accurate as long as you follow the instructions correctly. The NHS says a positive test result is almost certainly correct.
A negative test result is less reliable. The result may not be reliable if you do not follow the instructions properly or if you take the test too early.
If you get a negative result and still think you are pregnant, the NHS advice is to wait a few days and try again. Speak to your GP if you get a negative result after a second test but your period has not arrived.
Can contraception or medicines affect the result?
A pregnancy test will still work if you are on the pill. Some methods of contraception, such as the contraceptive pill, contain hormones, but the NHS says these hormones will not stop a pregnancy test working.
No method of contraception is completely effective, so it is important to take a pregnancy test if you think you might be pregnant, even if you have been using contraception.
The NHS also notes that some medicines can affect the results. If you are taking medicine and are unsure whether it could affect a test, a pharmacist or GP can advise you.
Where can you get a pregnancy test?
You can buy pregnancy testing kits from pharmacists and some supermarkets. They can give a quick result and you can do the test in private.
Free pregnancy tests are provided by sexual health services, by some young people’s services and by Brook centres for under-25s. You may also be able to get a pregnancy test free of charge from your GP.
For details of young people’s services, the NHS gives the national sexual health helpline number, 0300 123 7123. These services are confidential.
What should you do after the result?
If you are pregnant and plan to continue with the pregnancy, the NHS says it is important to tell the NHS as soon as possible after you find out. This is so you can get the care and information you need. You can do this by referring yourself for NHS pregnancy care with a midwife.
If you have a long-term health condition or are taking medicine, the NHS advises seeing a GP or specialist as soon as possible to discuss any changes to your care or medicine. It also says not to stop taking medicine that has been prescribed without talking with a doctor.
If you are not sure about continuing with the pregnancy, you can discuss this confidentially with a healthcare professional, such as a GP or a nurse at your GP surgery. Sexual health services can also give accurate, confidential information.
What you can do if you think you might be pregnant
- 1Work out when your next period is due, if you can.
- 2If your period is late, you can test from the first day of the missed period.
- 3If you do not know when your period is due, wait until at least 21 days after you last had unprotected sex.
- 4Read the instructions that come with the test and follow them exactly.
- 5If the result is negative and you still think you are pregnant, wait a few days and test again.
- 6Speak to a GP if a second test is negative and your period has still not arrived.
If you think you might be pregnant, these steps follow the order of the NHS advice on doing a pregnancy test.
These steps can help you get a reliable result, but they cannot tell you what a result means for your wider health. A GP, pharmacist or sexual health clinic can help with questions about your own situation.
Common Misconceptions & Clinical Facts
"You have to do a pregnancy test first thing in the morning."
The NHS says you can do a pregnancy test on a sample of urine collected at any time of the day. It does not have to be in the morning.
"A pregnancy test will not work if you are on the pill."
Some contraception contains hormones, but the NHS says these hormones will not stop a pregnancy test working.
"A negative pregnancy test always means you are not pregnant."
A negative result is less reliable than a positive one, particularly if the test was taken too early or the instructions were not followed properly.
Practical context and next steps
It can help to know that early signs of pregnancy do not start straight away. The NHS says symptoms and early signs usually start when you are around 4 to 6 weeks pregnant, and not everyone has all of them. A missed period, feeling or being sick, feeling extremely tired and sore breasts are among the signs the NHS lists.
If the unprotected sex was within the last few days, a pregnancy test will not be reliable yet, but emergency contraception may still be an option. It needs to be used within 3 to 5 days after unprotected sex, depending on the type, so a pharmacist, GP or sexual health clinic is the right place to ask promptly.
A decision checklist for this topic
Before acting on anything you read here, run through this short check.
Most tests can be used from the first day of a missed period.
If you do not know when your period is due, test at least 21 days after unprotected sex.
You can test at any time of the day.
A positive result is almost certainly correct.
A negative result is less reliable, especially if the test was taken too early.
After a second negative test with no period, speak to a GP.
When to get professional or urgent help
•Speak to a GP if you get a negative result after a second test but your period has not arrived.
•Contact an NHS sexual health service for a free pregnancy test or confidential advice.
•Ask a pharmacist about pregnancy tests, or about emergency contraception if the unprotected sex was in the last few days.
•The national sexual health helpline is 0300 123 7123.
Safety note: Some symptoms need medical advice rather than a home test. The NHS says vaginal bleeding, stomach pain and pelvic pain are symptoms to look out for as they may be a sign of something more serious. If you are worried about your health at any time, it is important to get medical advice.
Professional advice can be useful if you are unsure when to test, what a result means or what to do next. Pregnancy tests, contraception advice and information about your options are all available through NHS services, and sexual health services are confidential.
Questions & Clear Answers
If you do not know when your next period is due, the NHS advises doing a pregnancy test at least 21 days after you last had unprotected sex. If you know when your period is due, most tests can be used from the first day of a missed period.
Some very sensitive pregnancy tests can be used even before you miss a period. However, the NHS says tests are most reliable from the first day of a missed period, and a test taken too early may give a result that is not reliable.
A positive test result is almost certainly correct. A negative test result is less reliable, and the result may not be reliable if you do not follow the instructions properly or take the test too early.
If you get a negative result and still think you are pregnant, wait a few days and try again. Speak to your GP if you get a negative result after a second test but your period has not arrived.
Most pregnancy tests are reliable from the first day of a missed period. If you do not know when that is, wait at least 21 days after unprotected sex. A positive result is almost certainly correct, while a negative result taken too early may not be. If a second test is negative and your period has still not come, a GP is the right next step.
References & Sources
Openlywell articles are compiled with reference to published guidance from international public-health authorities, professional colleges and peer-reviewed literature.
- [1]NHS — Doing a pregnancy test, page last reviewed 9 February 2022
- [2]NHS — Signs and symptoms that might mean you’re pregnant, page last reviewed 31 July 2026
- [3]NHS — What to do when you find out you’re pregnant, page last reviewed 3 February 2026
- [4]NHS — Emergency contraception, page last reviewed 31 January 2024
Was this article helpful?
Your anonymous feedback helps our clinical and editorial team keep guides accurate and clear.
Related Guides & Further Reading
More in BlogEmergency Contraception: Options, Timing and What to Do Next
Emergency contraception explained: the morning-after pill, ulipristal acetate, the copper IUD, why timing and ovulation matter, and what to do after unprotected sex.
Types of Birth Control: How to Compare Contraception Options
Compare the main types of birth control — implants and intrauterine contraception, combined and progestogen-only methods, barriers, fertility awareness and permanent options.
How to Put On a Condom: Correct Use, Protection and Common Mistakes
How to put on a condom correctly, what condoms do and do not prevent, lubricant compatibility, size and fit, the mistakes that cause failure, and what to do after a break.