Getting a positive pregnancy test can be an emotional moment—but in rare cases, the result can be false. A false-positive pregnancy test happens when the test says you’re pregnant even though you’re not.

This can occur for a number of reasons, including user error, recent miscarriage or abortion, certain medications, or underlying medical conditions. While home pregnancy tests are about 99% accurate when used correctly, mistakes and biological factors can sometimes lead to misleading results.

1. User Error

The most common cause of a false-positive pregnancy test is not following the instructions properly.

The 99% accuracy rate often cited for home tests comes from laboratory testing—not real-world conditions. Missteps like checking results too early or too late, using expired tests, or contaminating the urine sample can all cause incorrect readings.

Always follow the test’s timing and instructions carefully for the most accurate result.

2. Recent Miscarriage or Abortion

If you’ve recently had a miscarriage or abortion, your body may still contain detectable levels of human chorionic gonadotropin (hCG)—the hormone that pregnancy tests identify.

After a miscarriage, it can take 7 to 60 days for hCG levels to return to zero. During that time, you may get a false-positive result.

In some cases, an incomplete miscarriage (when tissue remains in the uterus) can cause prolonged hCG elevation.

See a healthcare provider immediately if you experience:

  • Heavy or persistent bleeding

  • Severe cramping

  • A gush of vaginal fluid

  • Tissue passing from the vagina

These could signal retained pregnancy tissue requiring medical care.

3. Medications

Certain medications can interfere with pregnancy test accuracy—especially fertility drugs that contain hCG.

Examples include:

  • Pregnyl

  • Ovitrelle

  • Predalon

These drugs artificially raise hCG levels, sometimes leading to a false-positive test.

Additionally, some antidepressants, particularly SSRIs (selective serotonin reuptake inhibitors), may rarely cause interference, though more research is needed.

4. Medical Conditions

Although uncommon, several health conditions can cause elevated hCG levels even when a person isn’t pregnant.

These include:

  • Certain cancers: such as uterine, ovarian, lung, liver, pancreatic, or breast cancer

  • Heterophile antibodies: proteins that react with animal antigens used in lab tests

  • Immunoglobulin A (IgA) deficiency: low or absent antibody levels

  • Rheumatoid factors: immune proteins that mistakenly attack healthy tissues

Hormonal changes during perimenopause or menopause can also mimic pregnancy hormone patterns and cause false-positive results.

5. Evaporation Lines

If you wait too long to read your test, you may see a faint “evaporation line,” which can be mistaken for a positive result.

This happens when urine dries and leaves a line where the test dye once was—creating the illusion of a positive test.

To avoid this, always:

  • Read the result within 10 minutes

  • Use tests that display words like “Pregnant” or “Not Pregnant” for clarity

6. Chemical Pregnancy

A chemical pregnancy occurs when a fertilized egg implants but stops developing very early. It can cause a temporary rise in hCG that triggers a positive test—only for levels to drop soon after.

Up to 15–20% of conceptions may end this way, often before the person realizes they were pregnant.

While emotionally difficult, chemical pregnancies are common and typically not harmful to future fertility.

7. Ectopic Pregnancy

An ectopic pregnancy happens when a fertilized egg implants outside the uterus, usually in a fallopian tube. Although the pregnancy is not viable, the body still produces hCG, which can trigger a positive result.

Ectopic pregnancies are medical emergencies. Seek immediate care if you experience:

  • Sharp pelvic or abdominal pain

  • Vaginal bleeding

  • Shoulder pain

  • Dizziness or fainting

Prompt treatment is essential to prevent complications.

8. Molar Pregnancy

A molar pregnancy (gestational trophoblastic disease) occurs when abnormal tissue grows in the uterus instead of a healthy embryo.

There are two types:

  • Complete molar pregnancy: No fetus develops—only abnormal tissue

  • Partial molar pregnancy: A malformed fetus and abnormal tissue grow together

In both cases, hCG levels are extremely high, producing a positive pregnancy test even though the pregnancy isn’t viable.

Medical treatment—often surgical removal—is necessary to prevent further complications.

How Home Pregnancy Tests Work

Home pregnancy tests detect hCG in your urine, which your body starts producing shortly after fertilization. Levels peak around 10 weeks of pregnancy.

For best results:

  • Take the test with first-morning urine, when hCG concentration is highest

  • Follow all instructions carefully

  • Wait the recommended time (usually 2–3 minutes) before reading results

  • Avoid expired tests

A positive result may appear as two lines, a plus sign, or the word “Pregnant”—depending on the brand.

Accuracy of Home Pregnancy Tests

When used correctly, most home pregnancy tests are about 99% accurate. However, timing matters—tests are most reliable 1–2 weeks after a missed period.

For earlier confirmation, a blood test performed by a healthcare provider can detect lower levels of hCG and confirm pregnancy sooner.

What To Do If You Get a Positive Pregnancy Test

If you get a positive test result:

  • Schedule an appointment with an OB-GYN or midwife to confirm pregnancy through blood tests or ultrasound.

  • Avoid assuming the test is wrong—false positives are rare.

  • If you suspect an error, recent miscarriage, or health condition, your provider can perform additional tests to determine the cause.

If you’re trying to conceive, early medical care ensures the healthiest start for both parent and baby.

A Quick Review

A false-positive pregnancy test can occur for various reasons—most often from user error, hormone fluctuations, fertility drugs, or certain medical conditions.

While rare, these results can be confusing and emotionally challenging. To confirm pregnancy or rule out underlying issues, always follow up with a healthcare professional for proper testing and guidance.