When is a patient considered iron deficient?
Iron studies consist of serum iron, TIBC/transferrin, and ferritin. It is acknowledged that ferritin is the most sensitive measure, and a ferritin <25 mcg/L is highly suggestive of iron deficiency, and probably that a ferritin <100 mcg/L signals milder deficiency.
They do NOT have to be anemic to be considered iron deficient! Anemia only occurs when iron deficiency becomes more severe.
Do I have to get any other tests if someone is iron deficient?
Iron deficiency anemia is a symptom, not a diagnosis! It reflects something else going on in the body. Iron may be lost through the GI tract, or urinary or respiratory tracts. It may be decreased with inflammation (mixed iron deficiency-anemia of chronic disease is not uncommon). It may be lost through dialysis. Iron deficiency anemia may prompt EGD/colonoscopy or any other number of tests for a workup of blood loss.
I’ve always given patients oral iron and hoped for the best. What’s wrong with oral iron?
There’s nothing wrong with trying oral iron if someone has low-moderate iron deficiency (if they are very depleted, then IV iron should be the first choice). It’s recommended to trial oral iron for a month.
However, oral iron is not well-tolerated by about 70% of patients. Nausea, constipation, and dark stools are common. It tastes gross. It might not be well absorbed in the setting of other medications (PPIs, for one). Furthermore, a patient with a malabsorptive condition or inflamed gut will not absorb as much iron through the GI tract, clearly.
The “slow-release” iron formulations do not actually lead to more absorption. And one common method, prescribing iron three times a day at meals, actually decreases the overall absorption of iron!
I thought IV iron was associated with anaphylaxis.
It’s very rare. It happens in 1 out of 200,000 cases. Compare that to penicillin reactions, which happen in 1 out of 5,000 cases. If you are willing to give someone a penicillin-based drug, you should also be willing to give IV iron.
Ok, my patient is getting IV iron. When can I check their labs to see if it worked?
Ferritin levels can be checked 8-12 weeks after infusion. (If it’s checked too early, you will get a falsely elevated result.)