Should someone who is not pregnant have hcg in their blood? does a small amount of hcg weeks before the missed period indicate one could be pregnant?

No & maybe: Hcg should only be present in someone who is pregnant. +hcg weeks before menses could indicate an early pregnancy, there are also uncommon tumors of the ovary that can cause +hcg levels in patient who are not pregnant. (a couple of other very rare conditions can cause also). And, lastly, people who use HCG administration for weight loss will have + levels in their system.

Hcg: If you are not pregnant and you have a detectable level of hcg, then you should be checked for the presence of a tumor that secrets hcg, because having HCG elevations apart from pregnancy is not normal.

Possibly: Hcg levels are never "0". It is when they are more than certain level that pregnancy or a possible rare tumor is present. It depends on your results. Talk to your clinician.