Understanding Low Beta HCG Levels & Pregnancy Possibilities

Question
QUESTION: I had a quantitative beta hcg blood test 3 weeks after intercourse and the value was less than 1 not pregnant. Is it possible to be pregnant but not have any hcg in the blood? I am having some symptoms and had a very light bleed when I was expecting my period. Or does this value mean that I cannot be pregnant?

ANSWER: AA

Although hCG levels are not reliable in diagnosing pregnancy, a level less than 1 means you are not pregnant.

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QUESTION: Dr then what do you consider a reliable way to diagnose pregnancy?? I thought hcg home and blood pregnancy tests are extremely accurate. Also, I have pcos- is it possible to develop cysts while on hormonal birth control? I have switched to a lower dose of progestin and estradiol from my last brand and I'm worried that my cysts could be developing again. Thank you so much for your help

Answer
AA

No way you can be pregnant if your hCG in blood is less than 1 with pcos and you are taking the pill. These light symptoms you talk about can be due to the pill. The pill contains hormones similar to those of pregnancy and can produce symptoms similar to early pregnancy. Ultrasound is the best way to diagnose pregnancy if in suspicion.

Good Luck