When to Take a Pregnancy Test: Timing, Time of Day and False Negatives

When should you take a pregnancy test?

Take a home pregnancy test from the first day of a missed period: the NHS says that is when pregnancy tests are most reliable, and the US Office on Women's Health says you can test as soon as that day. Some very sensitive tests can be used before a missed period, but the NHS warns that a test taken too early may not give a reliable result.

All pregnancy tests detect a hormone called human chorionic gonadotropin (hCG), the NHS explains. The Office on Women's Health says that the amount of hCG in your urine rises with time, so the earlier you test, the harder it is for the test to detect it. For the most reliable result, the FDA says to test 1 to 2 weeks after a missed period.

The NHS lists sore breasts, tiredness and feeling sick among the early signs of pregnancy, and notes that not everyone has all of them.

How soon can a pregnancy test show you are pregnant?

A urine test typically shows a pregnancy 2 weeks or more after conception, the Office on Women's Health says. The FDA says that with a 28-day cycle, hCG can be detected in urine 12 to 15 days after ovulation.

A test turns positive only once your body is making hCG, which the Office on Women's Health says happens after a fertilized egg implants in the uterus, usually about 10 days after conception. The NHS says hCG starts to be produced around 6 days after fertilization.

Some newer tests say they can be used 4 or 5 days before your period is due. According to the Office on Women's Health, even these tests claim their best accuracy only after the date of your expected period.

A blood test at a doctor's office can detect a pregnancy earlier, about 10 days after conception, the Office on Women's Health says. Its quantitative version, also called a beta hCG test, measures the exact amount of hCG. hCG levels by week explains what those numbers mean.

What is the best time of day to take a pregnancy test?

MedlinePlus says to use your first urine of the morning for the most accurate result, because morning urine usually has more hCG than urine later in the day. The FDA and the Office on Women's Health also say first-morning urine improves accuracy. The NHS says a test can be done on urine collected at any time of day and doesn't have to be in the morning.

MedlinePlus advises against drinking large amounts of fluid before you collect the sample, because that can dilute the hCG so it may not show up. The Office on Women's Health recommends checking the expiration date and waiting up to 10 minutes before reading the result window.

Can a pregnancy test be negative even if you are pregnant?

Yes, a home pregnancy test can be negative even though you are pregnant if you test too soon, MedlinePlus explains, because your body has not yet made enough hCG to show up. The NHS says a positive result is almost certainly correct, while a negative result is less reliable. The FDA estimates that 10 to 20 out of every 100 pregnant women will not detect their pregnancy on the first day of their missed period, because many have irregular periods or miscalculate when their period is due. The Office on Women's Health adds that in up to 10% of women, implantation does not happen until after the first day of a missed period.

If the test is negative and your period still hasn't come, test again. The NHS and the Office on Women's Health say to wait a few days, and MedlinePlus suggests repeating the test a week after the first one. The NHS advises speaking to your doctor (your GP in the UK) if a second test is negative and your period has not arrived.

The Office on Women's Health says that however faint the line or plus sign, if you see it you are most likely pregnant. A blank control line means the test did not work and should be repeated.

A home test can, in some cases, show you are pregnant when you aren't, MedlinePlus says, and fertility medicines are one cause. The Office on Women's Health names medicines with hCG as an active ingredient, such as certain infertility medicines, and says most other medicines, including birth control and antibiotics, should not affect a home test.

When should you test if your periods are irregular?

With irregular periods, the Office on Women's Health suggests testing 36 days after the start of your last period or four weeks after you had sex. The NHS says that if you don't know when your next period is due, you should test at least 21 days after you last had unprotected sex.

The Office on Women's Health counts periods as irregular when they come less than 21 or more than 35 days apart, or when cycle length changes from month to month. If the result is negative and you still think you may be pregnant, it advises waiting a few more days and testing again, or calling your doctor for a blood test.

What should you do after a positive pregnancy test?

After a positive test, contact a doctor or midwife to start prenatal care. The Office on Women's Health advises calling your doctor for an appointment, where a blood test can confirm the pregnancy. In the UK, if you plan to continue the pregnancy, the NHS asks you to tell it as soon as possible, and you can refer yourself for NHS pregnancy care with a midwife.

The first prenatal appointment covers when it usually happens and which tests to expect. If you are not sure about continuing the pregnancy, the NHS says you can talk it through confidentially with a healthcare professional.

When should you call your doctor or midwife?

The NHS says symptoms of an ectopic pregnancy, where the pregnancy grows outside the uterus, usually develop between the 4th and 12th weeks of pregnancy. It advises getting medical advice if you have these symptoms and think you might be pregnant, even before a positive test. Call your doctor or midwife if you have:

• Vaginal bleeding after a positive test. ACOG says vaginal bleeding is sometimes the only sign of an ectopic pregnancy, and to call your OB-GYN right away if you have it.
• Belly pain, typically low down on one side, which the NHS lists as an ectopic symptom. The NHS notes that tummy pain has many other causes; cramping in early pregnancy covers them.
• Pain at the tip of your shoulder, where the shoulder ends and the arm begins. The NHS says to get medical advice about this right away.
• Pain or pressure in your bottom when you poo, pain when you pee, or diarrhea. The NHS lists these as possible ectopic symptoms too, and says to get advice if you have them and think you might be pregnant.
• A second negative test and still no period (NHS).
• A positive result while you are taking fertility medicines, which MedlinePlus says your provider may need to check.