Hi, I'm 27 years old my last LMP was 8 jan 2015 and I checked on 8 feb I got positive in urine test and went to doc she has done a vaginal scan no sac has seen and then she said for blood beta test that also came positive with 416 miu/ml and then she said that to do the test after 2 days. So my question is this range is good for 4 weeks 0 days and why the sac did not seen and this range can be doubled. please tell me.