Can Pregnancy Tests Give a False Negative?

Can Pregnancy Tests Give a False Negative?

Have you missed a period and taken a pregnancy test only to find just one blue line? It can be a confusing time, especially if you’ve been experiencing other symptoms that indicate you could be expecting. Is a negative pregnancy test always accurate? Or is there such a thing as a false negative pregnancy test?

Here, we take a closer look at how trustworthy the results of a home pregnancy testing kit really are and examine the potential pitfalls associated with home testing.

The Test Is Negative – Did I Take It Too Soon?

There are a number of home pregnancy testing kits for sale these days that claim to give you accurate results from the day you miss a period. Some even claim to give you an accurate result before that date. So, does that mean a negative result from one of these tests is genuine?

Not necessarily. Your results will be more accurate if you wait longer before you test. Why? A short while after the fertilized egg has attached to the lining of the uterus during implantation, the placenta will begin to form and start to produce the pregnancy hormone HCG (human chorionic gonadotropin). This then enters the bloodstream and your urine.

In the early stages of pregnancy, the concentration of HCG in your body will increase rapidly. It will double every 2-3 days. That means that if you take a test on the day you miss your period it may be harder to detect the HCG in your urine stream. If you wait just a few days, though, the level of HCG will be much higher and so you’re more likely to see the accurate result.

Bear in mind, too, that your ovulation may occur at different times each month. This means that the fertilized egg may implant in your uterus at varying times. As a result, the HCG production may begin later than you expected, and it may not be detectable on the day your period was due. Also, if you suffer from irregular periods, you may have miscalculated the date on which you were due to menstruate.

If it’s vital to confirm immediately that you’re pregnant you should visit your healthcare provider to get another urine test carried out that can be sent to a lab. You may also be given a blood test measuring the level of HCG in your bloodstream or you may even be offered an ultrasound scan to confirm whether or not you have conceived.

What Does a Negative Pregnancy Test Look Like?

One thing that causes a lot of confusion amongst women is that different pregnancy tests have different ways of showing their results. This can lead to misinterpretation of the symbols that appear. Home testing kits that show a line to indicate a positive result are especially hard to interpret. If the control line develops but the second line is very faint, it can be difficult to determine whether or not that is a positive result. Experts say that if you see any line in the second window, even if it’s extremely faint, the answer is that you’re very likely to be pregnant.

The line may be very faint due to a low level of HCG in your urine. This can happen because you are only at a very early stage of your pregnancy. The most sensitive kits are capable of detecting pregnancy at an extremely early stage, some even from five days before your period would be due, but at that point, the HCG level is so low that any line that appears will be extremely faint. When your pregnancy advances, the HCG level will rise. Therefore, if you wait a few days then take another test, the positive line should be a lot stronger and more visible.

Could the Pregnancy Test Stick Be Faulty?

Most pregnancy tests taken at home involve placing a dipstick into the stream of urine or dipping it into a pot of urine that you’ve collected. Within a few minutes, the dipstick will show the result. Sometimes, this will appear as lines, a plus or minus sign, or even as the words “not pregnant” or “pregnant”.

It’s important to always read the instruction for the test that you’ve purchased thoroughly before you check the result. You need to wait for the appropriate amount of time for the result to appear. This will usually be at least 2 minutes. The majority of tests come with a control indicator, with a symbol or line appearing in a result window. If that symbol or line fails to appear within the appropriate time, the test is faulty. You will need to repeat the test with a different dipstick.

Some tests will also be more sensitive than others, with some tests capable of detecting a lower level of HCG in your urine than others. Make sure that you’ve checked the expiry date of the test too before taking it – an expired test may not show an accurate result.

Are Home Pregnancy Tests Accurate?

If you read the box of a home pregnancy test, you’ll probably see that it claims to be about 99% accurate. Yet, they all different in how early they’re able to detect a pregnancy in a woman who has only recently missed her period. Therefore, if your result is negative, but you’ve reason to believe you could be pregnant, you should take another test 7 days after missing your period.

Is My Medication Affecting My Test Result?

There are some medications such as fertility drugs which contain HCG. These could interfere with the result of your home pregnancy test. Most other medications, though, including birth control and antibiotics, won’t have any effect on your test’s accuracy.

My Test Was Negative but It Was Wrong. Why?

Although we tend to trust the medical items that we buy in stores and pharmacies, in fact sometimes home pregnancy tests can give an incorrect result. You may, therefore, see a negative result even if you are pregnant after all. If this has happened to you, you may be wondering why you got a false-negative result. There are a few reasons why this may have occurred, including:

  • You took a test too soon. If you take a test just after missing your period it may be hard for the test to detect the HCG level in your urine. Wait a few days before testing or repeat the test a week after you missed your period. If you’re unable to wait, ask your doctor if you can take a blood test that will confirm whether or not you’re actually pregnant.
  • You checked the result too soon. You need to give a pregnancy test enough time to work. Check the packaging to see how long you need to wait for the result to appear and set a timer.
  • You used diluted urine. The most accurate result can be obtained while your urine is concentrated. Take your test straight after getting up in the morning before drinking anything.

Could My Positive Pregnancy Test Result Be Inaccurate?

If your pregnancy test has shown a positive result it will usually be accurate. However, there are a few cases in which a false-positive may appear. This may occur if:

  • You lost the pregnancy at an extremely early stage after the fertilized egg had implanted. This is known as a biochemical pregnancy.
  • You took the test too early after taking fertility drugs containing HCG.
  • You’re experiencing a problem with your ovaries.
  • Menopause or ectopic pregnancy can also cause an inaccurate result to appear.

Bear in mind, though, that it is very rare for a pregnancy test to show a positive result if you aren’t pregnant. While false-negatives are more common, false-positives only occur in a handful of cases.

What Do I Do Next?

If you have received a negative result on your home pregnancy test but still think you may be pregnant, there are a few steps you should take:

  • If your period hasn’t started within a week, take a second test to see if you get a different result.
  • If you get a second negative result but you still have no period or you experience other pregnancy symptoms, speak to your doctor. There are a few factors that can cause a missed period. These include low bodyweight, thyroid disorders, problems with your ovaries, stress and excessive exercise. If you really aren’t pregnant, your doctor will give you advice and help you to get your periods back to normal.

If your second test is positive or you take a number of tests and find you get mixed results, visit your physician. You may need to take a blood test to confirm you’re pregnant or you may be offered an ultrasound that will give you a definitive answer. The earlier your pregnancy can be confirmed, the earlier you can start receiving good pre-natal care.