I started taking ferrous fumerate 210 mg three weeks ago. i just had a blood test which shows my hemoglobin conc had dropped by 15, hct dropped by 3. what are the likely reasons for this and will it increase eventually?

When you post on this site, please include the units of measure with your numbers. In the US grams of hemoglobin/deciliter is the normal unit used. If you dropped 15 you would be dead. If using grams/liter, the issue is one of why you are losing instead of gaining. Your doc should investigate a reason for chronic blood loss.

A drop in your hematocrit, while taking iron suggests that there is continuing blood loss. If you are not losing excessive blood through menstrual bleeding then internal bleeding, usually in the intestine, needs to be investigated. You should consult your doctor at the earliest. Wish you good health!