Serum ferritin at 6ng took ferrous sulfate 310 mg 3x a day retest every 2 weeks - 18ng then 2 weeks after 27ng - then 54.6ng recently dropped to 25 again - what caused it? what doctor shld i see?

How do you feel?: Monitoring symptom improvement is more important than chasing numbers, especially if hemoglobin/hematocrit normal. If were ill during the 1st two tests, the ferritin could have been falsely or "reactively" elevated. If you had your cycle, that too could explain the subsequent downward trend. Can see int med, gi, or hematologist. Vitamin c helps with absorption. A diff formulation may work better.

Treating patient: It's really hard to give sound advice based on your presentation. Numbers is one thing, but really treating the patient as a whole is different. Ferritin is by far the least sensitive measurement of blood related problems as it is as it can fluctuate based on the amount of inflammation in your body. What is your complete blood count, iron level, binding capacity? And what are your symptoms?