What can cause a false negative beta-hCG result?

A false negative result of a beta-hCG test can be obtained when the test was performed too early. Measurement error is also potentially possible, however, this is very rare. Drugs do not falsify beta-hCG results (except for drugs containing hCG). I enclose a thread in which a similar topic was raised: https://www.gdziepolek.pl/opinie-i-pytania/98152/czy-sa-na-swiecie-takie-przypadki-ze-beta-jest-cala-ciaze-ujem

To @KajaXX:

Taking ellaOne may cause menstrual bleeding to occur later.

A blood beta-hCG test at least 10 days after intercourse is reliable and there is no need to repeat the test.

We wrote more about pregnancy tests in the article:

https://www.gdziepolek.pl/artykuly/test-ciazowy-jaki-wybrac-i-kiedy-zrobic

Hello, is the result after the 18th day after intercourse reliable and 3 days before the planned menstruation? The result came out <0,100. Dodam ze w tym miesiącu przestałam brać antykoncepcję hormonalna i po stosunku z niepewności przyjęłam ella one. Czy w tym przypadku można wykluczyć ciąże? Miesiączki nadal brak, czy wina stoi bo otrzymaniu tak dużej dawce hormonów? Czy trzeba wykonać ponownie test?

To @Cecylia: Exactly.

So withdrawal bleeding excludes and does not happen during pregnancy?

To @Cecylia: Yes, you can rule out pregnancy.