Question: how long does hcg stay in your system after injection?
Answer: Typically, it takes about 10 days for the drug hCG to clear from blood and urine. So, if you do an UPT too soon — 10 days or less after the hCG injection — you may get a false positive because you are detecting the medication that is still in your blood and urine, not the hCG that a pregnancy is making.