Do i need to repeat quantitative beta hcg blood test if i get <0.1miu/ml at 5 weeks after intercourse?or can i rule pregnancy out?

If 5 weeks after sex: Pregnancy tests are very accurate and not affected by foods, herbs, common illnesses, sexually transmitted diseases, vaginal spotting, or medications. A urine test gives a reliable result 3 weeks after last sex or 1 week after missing a period. A blood test should be positive a few days or a week earlier than that, but one need not do a blood test. Urine tests are very accurate and cheap to do.