Is it possible for a pregnancy test strip to fail to detect a one-month pregnancy?

Under normal circumstances, pregnancy may not be detectable one month after conception if fertilization occurred late, the urine is diluted, or the pregnancy test strip has low sensitivity. However, if conception happened early, the urine is concentrated, and a reliable test strip is used, pregnancy can usually be detected. If in doubt, it is recommended to consult a healthcare provider early. Detailed analysis is as follows:

If conception occurred late (e.g., ovulation delayed by more than a week), human chorionic gonadotropin (hCG) levels may not yet have reached the detection threshold of the test strip one month after conception. Additionally, drinking large amounts of water before testing can dilute the urine and lower hormone concentration, leading to a false-negative result. Furthermore, if the pregnancy test strip has been improperly stored (e.g., exposed to moisture), is expired, or has low sensitivity, its accuracy may be compromised, resulting in an undetectable outcome.

If conception occurred early (with normal and timely ovulation), hCG levels are typically high enough to be detected one month after conception. Using first-morning urine (which has higher hormone concentration), a valid and properly functioning pregnancy test strip, and following correct testing procedures generally yields a positive or faintly positive result, making it unlikely that the test will fail to detect pregnancy in such cases.

It is recommended to use first-morning urine for testing and to avoid drinking large amounts of fluid beforehand. If the first test is negative but menstruation has not started, retesting after 3–5 days is advised. If multiple test results are unclear or if any discomfort occurs, medical consultation and blood hCG testing should be sought to confirm pregnancy status and prevent delayed diagnosis.