Negative Pregnancy Test Turned Positive After Several Hours – 4 Reasons Why

Taking a pregnancy test is relatively straight forward: you pee on a stick and then it shows you whether you are pregnant. But what if your pregnancy test results change in a matter of a few hours? What can cause that?

In this article:

• How Do Pregnancy Tests Work?
• Why Did My Pregnancy Test Results Change From Negative to Positive in Several Hours?
• How Can I Avoid Incorrect Pregnancy Test Results?
• Ultimately…

Before we find out what can cause a pregnancy test result to change from negative to positive over a few hours, we must first understand how pregnancy tests work.

How Do Pregnancy Tests Work?

Home pregnancy tests are accurate tools used for detecting pregnancy.

Pregnancy tests work by testing your urine for the presence of a hormone called human chorionic gonadotropin (hCG).

The hCG hormone begins to be produced after implantation occurs- the process where a fertilized egg implants into the lining of your uterus. It is through this connection, that the fertilised egg (or blastocyst) receives the nutrients and blood supply it needs to grow.

If your hCG levels are high enough in your urine (usually around 2 weeks after conception), the pregnancy test will dispaly a positive result.

Positive pregnancy test results can be shown by a cross, two lines (a test line and a control line), or even the word “pregnant”- depending on the kind of pregnancy test you choose.

But what can cause pregnancy test results to change? Read on to find out.

If you are trying to decide what type of pregnancy test to use, why not check out our article: Are Digital Pregnancy Tests More Accurate?

Why Did My Pregnancy Test Results Change From Negative to Positive in Several Hours? – 4 Reasons Why

1) You Left Your Test For Too Long

It is important to always follow the pregnancy test instructions, as not following the pregnancy test instructions, or following them incorrectly, can give you incorrect pregnancy test results.

Pregnancy test results are only valid for a certain amount of time- usually around 10 minutes- so if you leave your pregnancy test out for several hours, and notice that your negative test result has changed to a positive test result, you should just disregard the changes, as they are most likely inaccurate.

This is because, over time, the urine within the result window begins to dry- which causes an evaporation line (faint line) to appear. This can easily be mistaken for a faint positive pregnancy test result.

2) Your Urine Was Diluted

During early pregnancy, if you have taken a pregnancy test and received a negative result, and took another pregnancy test and received a positive pregnancy result several hours later, it may be due to the amount of fluids you are drinking.

If you drink a lot of fluids, it can dilute your urine- decreasing your hCG levels in your urine, which can cause a negative pregnancy test result to be shown.

If you have recently had your implant removed, you can read our article on When to Take a Pregnancy Test After Implant Removal?

 

3) Evaporation Line was Mistaken for A Faint Positive Result

Evaporation lines can be pesky things! They can look like a positive faint test line, whilst they are not a positive result at all!

Evaporation lines are the product of the urine drying on the home pregnancy test, which causes the results window to show a faint line.

If you are unfamiliar with evaporation lines, you may mistake them for a positive test line.

We have an article on evaporation lines vs faint positives to help you to tell the difference.

 

4) It Was A False Positive Result

It may be that the pregnancy test result you received later on in the day may have been a false positive. False positive pregnancy test results are caused by a variety of things, including:

• Following the pregnancy test instructions incorrectly
• Using an expired pregnancy test
• Using an unreliable brand
• Other unknown reasons.
• Did you know twins can cause a false negative test result?

How Can I Avoid Incorrect Pregnancy Test Results?

• Check the Expiry Date. If you are taking a pregnancy test, it is important to make sure that the pregnancy test has not expired. Once a pregnancy test expires, the antibodies within pregnancy test, which detect the hCG, begin to break down. This can cause a negative result to be shown, when you are actually pregnant.
• Follow the instructions carefully. Following the pregnancy test instructions carefully is crucial to receiving accurate test results. It is important to note whether you should take a urine sample and dip the pregnancy test, pee directly onto the pregnancy test, when you should read the results, and when the results should be rejected.
• Take the pregnancy test in the morning. Taking a pregnancy test with the first morning’s urine can help you to receive the most accurate pregnancy test results- this is because your hCG levels are the most concentrated, so if you are still in early pregnancy, you are more likely to receive a true positive test result.
• Wait until your hCG levels are high enough. We know how difficult the two week wait can be- however, it is there for a reason! Taking a pregnancy test kit too early can give you a negative result, even when you actually are pregnant!

 

Ultimately..

Ultimately, if you are unsure of your pregnancy test results, you should take a test again in a few days time to avoid inaccurate results. If you received a positive test result and then negative 2 hours later, we have an article on that too which you can read. If you have had a faint positive pregnancy test and then negative the next day, there are plenty of reasons for that too.