In patients with iron deficiency due to history of gastric bypass or IBD, would you consider oral iron therapy if the iron deficiency anemia is mild?   

Oral iron can often be effective in iron deficiency, as long as absorption is intact. If you are concerned about absorption, performing an oral iron challenge can be useful in allowing you to avoid long trials of oral iron that will be ineffective. Simply check an iron panel at baseline, then admini...

A trial of oral ferrous sulfate (often with a stool softener) given every other day is worth a try in patients with mild iron deficiency with or without anemia. Vitamin C by diet or supplement may help with absorption (DeLoughery et al., PMID 38864796). The optimal ferritin level may differ from per...

In patients with poor iron absorption or who are intolerant to PO iron, I normally put them on either transdermal iron or sublingual iron. These are generally well-tolerated and effective.

Oral iron supplementation following bariatric surgery is effective in approximately 50% of cases, with variable success rates likely attributable to poor patient adherence and impaired absorption. A systematic review found that while oral iron was most commonly used for prevention of iron deficiency...

I agree with this approach.  Just wanted to add that some of these folks do not respond to oral iron even if tolerating it (due to the gastric surgery).