Mam and sir Sir my friend took beta hcg blood test 2 times first on 27 october next day after missed periods it was negative then she again took beta hcg blood test on 30 that was positive...now my question is what can the the reason for the false hcg result before... So from this above incident i m forced to ask u when to take betah g test after missed periods or after 2 weeks of intercource which is more accurate and more relable...in above case if he would have consider that she is not pregrant then the senerio can be the worst...so plzz reply when is the best time to take beta hcg . . After 15 days of sex or after missed period. .