What causes low hemoglobin with bariatric surgery?

Low iron : Bariatric surgery reduces the bodies capacity to absorb nutrients including iron which is required to make hemoglobin. Many women are borderline anemic anyway if they have heavy periods for example & this can tip them over. You should take supplements after bariatric surgery.

Agree: Some may require IV iron therapy secondary to poor absorption depending on the type of surgery.

Absorption issue: After gastric bypass (not banding) your abiltiy to absorb b-12 and iron and you need to be on b-12 injections monthly and usually 2-3 years after bypass require IV iron infusions which may need ot be repeated as your iron sat% drops we usually monitor these patients regularly. In any case you nee dot have a complete work up for anemia to amke sure nothing else is going on.

Nutrients.: After bariatric surgery we can become deficient in iron and vitamin B12, both of which being vital for red blood cell production. So once deficient in these, we can become anemic (low hemoglobin). Supplementation and monitoring of these after surgery is mandatory.