Home pregnancy tests are designed to detect human chorionic gonadotropin (hCG), a hormone produced during pregnancy. They can provide an early indication of pregnancy, but the accuracy of a result depends on factors including when the test is taken and whether the instructions are followed correctly.
Most home pregnancy tests use a urine sample and include a control indicator to show whether the test has worked properly. A result can be negative even when a person is pregnant, particularly if the test is taken too early.
When to take a pregnancy test
Pregnancy tests generally become more reliable around the time a menstrual period is expected. Testing too early can produce a false-negative result because hCG levels may not yet be high enough for the test to detect.
People with irregular menstrual cycles may find it more difficult to determine the best time to test. In such cases, following the timing guidance provided with the specific test can help reduce the likelihood of an inaccurate result.
Some tests are marketed as being able to detect pregnancy before a missed period. Their ability to do so depends on the sensitivity of the test and the amount of hCG present in the urine.
Why a negative result may be wrong
A negative home pregnancy test does not always rule out pregnancy. Testing too early, using a diluted urine sample or not following the manufacturer’s instructions can affect the result.
If a test is negative but pregnancy is still suspected, repeating the test after several days or seeking medical advice can provide greater certainty.
A positive result, particularly when accompanied by a missed period, is generally a strong indication of pregnancy. A health professional can confirm the pregnancy and provide further guidance.
Read the instructions carefully
Home pregnancy tests differ in their design and instructions. Some use strips that are placed in urine, while others use different collection or testing methods.
Users should follow the instructions supplied with the particular product, including how to collect the sample, how long to wait before reading the result and how to interpret the control and test indicators.
The source material refers to tests with different strips, algorithms and multiple methods of calculating results. Those descriptions do not correspond to the way standard home pregnancy tests are generally interpreted, which typically involves detecting hCG rather than manually calculating a result.
It is also important not to confuse pregnancy tests with fertility monitors or other tests that track ovulation. Fertility tests generally look for hormonal changes associated with ovulation and are not substitutes for a pregnancy test.
IVF and pregnancy testing
Pregnancy testing may also be part of in-vitro fertilization (IVF) treatment. However, a home pregnancy test does not by itself confirm whether an IVF treatment has been successful.
After fertility treatment, timing can be particularly important because some medications used during treatment may affect pregnancy-test results. People undergoing IVF should follow the testing schedule provided by their fertility clinic.
