Home pregnancy tests are known for being reliable, boasting accuracy rates of up to 99% when used properly. However, like any test, false results can still occur. A false positive happens when the test shows that you're pregnant when, in reality, you're not.

Though rare, false positives are possible and may be due to a variety of factors, such as user error, early pregnancy loss, medical conditions, or certain medications.

1. User Error

Improper usage is one of the most common causes of false positive pregnancy results. While manufacturers test accuracy in controlled settings, at-home conditions may vary, which can affect outcomes.

One frequent mistake is misreading the test outside the recommended time window. Most tests instruct users to interpret results within 3–10 minutes. Waiting too long can lead to the appearance of an evaporation line, which may be mistaken for a positive result. Choosing a test that displays results as words—like "Pregnant" or "Not Pregnant"—can reduce this risk.

2. Chemical Pregnancy

A chemical pregnancy is an early pregnancy loss that occurs shortly after implantation. Although the pregnancy ends early, the body may have already started producing human chorionic gonadotropin (hCG)—the hormone detected by pregnancy tests.

Because hCG is present even for a short time, a test may pick it up and give a positive result even though the pregnancy has already ended. Chemical pregnancies are believed to occur in up to 20% of early conceptions.

3. Recent Miscarriage or Abortion

After a miscarriage or abortion, hCG can remain in the body for several days—or even weeks—depending on how far along the pregnancy was. As a result, a test may still show a positive result even though you're no longer pregnant.

In some cases, tissue may remain in the uterus, a situation known as an incomplete miscarriage, which can keep hCG levels elevated. Symptoms that may point to this include:

  • Bleeding (light or heavy)

  • Sudden fluid loss

  • Pelvic cramps

  • Passing tissue

Medical evaluation is important to ensure all pregnancy tissue is cleared to prevent complications.

4. Certain Medical Conditions

Some health conditions may cause elevated hCG levels even when pregnancy is not present. These include:

  • Ectopic pregnancy: When a fertilized egg implants outside the uterus.

  • Molar pregnancy: Abnormal growth of placental tissue in the uterus.

  • Certain cancers: Including cancers of the liver, lung, pancreas, bladder, and reproductive organs.

  • Autoimmune or hormonal disorders: Such as rheumatoid factors or IgA deficiency.

  • Heterophile antibodies: Which can interfere with lab test accuracy.

Additionally, women going through perimenopause or menopause may experience hormone fluctuations that lead to misleading test results.

5. Medications That Affect Test Results

Some medications—especially fertility drugs containing hCG—can produce false positives. These are commonly used during assisted reproductive procedures like IUI or IVF, and include brands such as:

  • Pregnyl

  • Ovitrelle

  • Predalon

There are also rare reports of antidepressants, particularly SSRIs, affecting pregnancy test results, although more studies are needed in this area.

If you're unsure whether your medications could be causing a false result, consult a healthcare professional.

How Pregnancy Tests Work

Pregnancy tests—whether urine or blood-based—detect hCG, which your body starts producing shortly after implantation. hCG levels typically double every 48–72 hours in early pregnancy and peak around 10 weeks after conception.

Several factors may influence test accuracy:

  • Test timing: Testing too early may result in low hCG levels that go undetected.

  • Cycle variation: If ovulation or implantation occurs later than expected, hCG might not yet be detectable.

  • Test sensitivity: Some brands can detect lower hCG levels and may give earlier results.

  • Proper usage: Following instructions closely is key to avoiding mistakes.

Tips for Taking a Home Pregnancy Test

To improve accuracy, follow these guidelines:

  • Use the first urine of the day, which typically contains the highest concentration of hCG.

  • Read the instructions carefully.

  • Either hold the test in your urine stream or dip it in a cup of collected urine, depending on the test design.

  • Wait the recommended time (usually a few minutes) before reading the result.

  • Avoid checking the result after the instructed time limit, as evaporation lines may appear.

  • Never use an expired test.

What To Do After a Positive Test

If you receive a positive result, schedule a visit with your healthcare provider, even if you’re unsure of the outcome. Early prenatal care is crucial to support a healthy pregnancy. Your provider can also determine whether the result is accurate, and check for conditions like early pregnancy loss or retained tissue after miscarriage.

It’s important to rule out serious causes like ectopic pregnancy, which require prompt attention.

A Quick Summary

False positive pregnancy tests are uncommon but can happen due to user error, early miscarriage, certain medical conditions, or medications. The most reliable way to confirm a pregnancy is through a blood test and medical consultation. Always follow up with a provider if you receive a positive result—whether expected or not—to ensure you get accurate information and proper care.