When can you take a pregnancy test (and how to read them properly!)

by Jane McGuire |

Whether you’ve been trying for a while, or have just noticed you’ve missed your period, working out when to take a pregnancy test can be difficult. As simple as it might sound (weeing on a stick that is), these little tests are actually far more complicated than that – from when you can take them to how accurate the result is, here’s all you need to know about pregnancy tests.

Read more: One week pregnant: advice and symptoms

When to take a pregnancy test

You can take a pregnancy test up to five days before your period is due. The early tests will promise to give readings ‘six days before your missed period’ – your missed period day is the day after your period is expected. During the early days of pregnancy, your hCG levels rise rapidly, so if you want as accurate a result as possible, do the pregnancy test on the day of your missed period. Whether positive or negative, the result will be over 99% accurate.

If you can, do the pregnancy test first thing in the morning as this is when your hCG levels will be at their highest. If this isn’t an option (or you want to do a test sooner rather than later), hold off going to the toilet for a few hours and then take the test. Avoid drinking lots of liquids to make yourself wee – this actually can dilute your urine and lower your hormone levels, increasing your chances of getting an incorrect result.

How to read a pregnancy test

Whatever test you choose, make sure you read the instructions carefully beforehand to ensure you fully understand what those little blue lines mean and ensure your pregnancy test is still in date (yes, they can go off).

Although each test might vary slightly, on all at-home pregnancy kits there should be two result windows. One of these is a test window, which should show a line before taking the test – this is simply a sign the test is working.

Once you’ve waited the allotted time, if your test has two windows, you’ll see a single line or two lines making a plus sign in the window. If there is a cross, you’re pregnant, if there is one line, you’re not.

If your test has a single window, normally the test line and the result line will appear side by side if you are pregnant. If not (and there is only one line in the window) you are not pregnant. It’s worth noting that even the faintest of lines can be an indicator that you are in fact pregnant.

How do pregnancy tests work?

A pregnancy hormone called human chorionic gonadotropin, or hCG, is produced by your body when you’re pregnant. ‘The levels of hCG begin to rise after fertilisation, and is what your pregnancy test picks up in your urine when the positive line appears,’ says GP Philippa Kaye. All pregnancy tests work by detecting this hormone, which increases in intensity as pregnancy progresses. Some tests can detect it earlier than others and display the results as either lines on non-digital versions or as words on digital tests.’

What are the earliest pregnancy tests I can take?

You can buy ultra-sensitive early result pregnancy tests which can now detect the pregnancy hormone up to five days before your period is due. It’s worth noting, you shouldn’t be disappointed if you get a negative result, as these tests are not always 100% accurate. Leading pregnancy test company First Response said that its early result pregnancy test detected the pregnancy hormone in 76% of pregnant women five days before their period was due, but in more than 99% of women three days before their period was due.

This is because the levels of hCG vary from woman to woman, and depending on when you do the pregnancy test, you may be pregnant, but just not have enough of the hormone to get a positive result.

How accurate are pregnancy tests?

According to the NHS ‘home pregnancy tests are accurate as long as you follow the instructions correctly. A positive result is almost certainly correct. However, a negative test result is less reliable. The result may not be reliable if you don’t follow the instructions properly or take the test too early.’

If the test is negative, ensure you check that you haven’t taken the test too early and if you think you might have, take another test in a few days. As we mentioned above, the level of hCG in your urine varies from woman to woman, so you might just need to wait a few days for your hormone levels to rise. If it’s positive, because home pregnancy tests are now so accurate you might find your GP doesn’t repeat the test when you go for an appointment.

It’s also worth noting, some medications can affect pregnancy test results. These include promethazine which is used to treat certain allergies, sleeping tablets, or medicines used to treat infertility. If you are worried about any medications you are taking, it’s a good idea to talk to your GP.

Will my GP do a pregnancy test too?

Your GP can do a blood pregnancy test which can also identify the presence of pregnancy hormone hCG. On a blood pregnancy test, the results will either show the exact amount of hCG in the blood, or confirm the presence of hCG in the blood. If you are pregnant, the level of hCG is determined to be between 5 and 25 mlU/ml. Normally you will be asked to do a second blood test 48 hours later, as in the early days of pregnancy your hCG levels double approximately every 48 hours. If the test is negative, the level of hCG will be under 5 mlU/ml.

Whilst pregnancy blood tests are not always necessary, if you are at higher risk for miscarriage or ectopic pregnancy, they might be recommended.

What are the early symptoms of pregnancy?

Dreaming of getting pregnant? You can find a comprehensive list of the early signs of pregnancy to look out for here, but put simply, the early signs and symptoms of pregnancy to look out for are as follows:

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1) Tiredness

This is one of the first signs of pregnancy to hit as your body gears up to start supporting your baby and can even start within two weeks of conceiving. If you're feeling extra exhausted and can't work out why, this could be a sign your body is getting ready to grow a baby.

What if I have symptoms of pregnancy but a negative test result?

As we mentioned above, sometimes home pregnancy tests can give an inaccurate result if they are taken too soon and your body has not yet produced enough hCG. Alternatively, you may have missed the very faint line on a pregnancy test and read it incorrectly. Finally, it might be worth checking that any medication you are on isn’t affecting the result.

My test has a faint line – am I pregnant?

A faint line means that the test has found the presence of the pregnancy hormone in your urine. If you have done the test correctly and made sure you’re not looking at the control line, then it means you are pregnant. Take another test in a few days’ time when there should be more of the pregnancy hormone to make the line stronger. If you’re worried about interpreting the tests correctly, you can buy tests that simply tell you 'pregnant’ or 'not pregnant’ - then you can be absolutely sure.

Related: False-negative pregnancy test explained

How do I work out when I conceived?

Some pregnancy tests have a conception indicator which tells you how many weeks ago you conceived, but if you've used a non-digital device, you can work it out for yourself. Your cycle starts on the first day of your period and is around four weeks long. Ovulation – when your body releases an egg – happens around two weeks into this, and the sperm needs to fertilise it within 48 hours for you to get pregnant.

Knowing when you conceived is how you work out how old your baby is in weeks, which is important when it comes to scans and appointments. Use our ovulation calculator if you’re not sure.

I’m pregnant, now what?

Congratulations, you’re pregnant! Once you’ve told your partner the big news, you’ll need to make an appointment to visit your GP so that they can register you with maternity services at your local hospital. They will send you a letter about a ‘booking in’ appointment when they will fill in all the relevant forms and make sure you have your screening assessments and free prescription and dental care information.

As daunting as it might seem, relax and spend these early days preparing yourself. Take a look at our pregnancy week by week to work out what your body and your baby is doing at each stage, and the common side effects to look out for.

Read next: one week pregnant: advice and symptoms

False positive pregnancy test: 6 possible causes

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