Is it safe to take iron supplements for fatigue or can it become toxic?

Hello doctor,

I began presenting last fall with some chronic fatigue. The initial blood work showed low iron saturation without anemia. I have attached reports of the same. There were other endocrine-related findings as well. In the course of various endocrine-related treatments and corresponding blood work, I began iron supplementation in the form of ferrous sulfate 143 mg daily. I began this before the blood work was done. So, you can see that that the levels have increased. Subsequent testing, a month later, showed a decline despite continuing treatment. Most recently, you can see that the levels are back up. Note that the ferritin levels began a bit low around 27 ng/mL and had increased to 30 ng/mL.

I have received a wide range of conflicting advice about whether low iron levels in the absence of anemia can cause fatigue. I have also received a range of conflicting advice about whether to continue iron supplementation. One doctor told me to continue taking the iron until the ferritin is up around 50 or so. Another said that would be unnecessary and to discontinue it and wait for three months to re-measure the blood work. It is all quite puzzling. Please help me to understand iron's role, if any, in fatigue in the absence of anemia. And help me to then understand the rationale for treatment or lack thereof. And finally, please give me some sense of when iron toxicity emerges in terms of blood work measurements and at what frequency one needs to check the iron levels during any supplementation.

Hello doctor,

Thank you for your answer. My endocrinologist and primary care physician both want me to continue taking the iron and resample the blood in three months. The idea is to raise the ferritin to about 50, so that I will have more iron reserves. I realize that this conflicts with your advice, but I want to understand this from a hematologist. Is continuing the iron safe? When does iron become toxic? Is toxicity going to occur right away or is it more of a long-term possibility? Is a 3-month waiting period sufficient for blood testing if I do continue the iron? They want me to take 143 mg ferrous sulfate per day during this time. These doctors seem very convinced that this is safe. Please help me feel the same way.