What you need to take for anemia depends on what’s causing it. Iron deficiency is by far the most common type, and most people with it need 150 to 200 mg of elemental iron per day from supplements. But anemia can also result from low vitamin B12 or folate, chronic disease, or blood loss that outpaces your body’s ability to recover. Getting the right diagnosis first matters, because taking iron when your problem is actually B12 deficiency won’t help, and vice versa.
Iron Supplements for Iron-Deficiency Anemia
Iron-deficiency anemia is typically treated with oral iron supplements, which come in three common forms. Ferrous fumarate contains the most elemental iron by weight at 33%, ferrous sulfate contains 20%, and ferrous gluconate contains 12%. “Elemental iron” is the portion your body can actually use, so two pills of different forms can contain very different amounts of usable iron even if the total milligrams on the label look similar.
Most adults with iron deficiency need 150 to 200 mg of elemental iron daily, which works out to roughly 2 to 5 mg per kilogram of body weight. Interestingly, taking iron every other day may actually improve absorption compared to daily dosing. Your body regulates how much iron it pulls in, and giving it a rest day between doses lets the absorption machinery reset. If your doctor recommends a specific schedule, it’s worth following closely rather than assuming more frequent doses are better.
Expect a slow process. Hemoglobin levels start climbing within the first couple of weeks, but fully replenishing your iron stores typically takes up to six months of consistent supplementation. A blood marker called ferritin reflects those deeper stores, and your doctor will likely recheck it to decide when you can stop.
B12 and Folate for Other Deficiency Anemias
Not all anemia is about iron. Low vitamin B12 or folate causes a different type called megaloblastic anemia, where your red blood cells grow abnormally large and can’t function properly. The treatment is straightforward: replace what’s missing.
For B12 deficiency, an oral dose of 1,000 mcg daily works well for most adults, as long as there’s no underlying issue with intestinal absorption. People with conditions that impair gut absorption (like pernicious anemia or Crohn’s disease) typically need B12 injections instead. Folate deficiency is treated with 1 mg of folic acid daily until levels normalize. One important caution: taking folate when B12 is actually the problem can mask the deficiency and allow nerve damage to progress, so testing for both before starting supplements is important.
How to Get More Iron From Food
Iron from animal sources (called heme iron) is absorbed at a rate of about 25%, while iron from plant sources is absorbed at 17% or less. Overall, people who eat animal products absorb 14% to 18% of the iron in their diet, while plant-based eaters absorb only 5% to 12%. This gap explains why vegetarians and vegans are at higher risk for iron deficiency even when their total iron intake looks adequate on paper.
Good plant sources include beans, lentils, spinach, fortified grains, nuts, and dark chocolate. Meat, poultry, and seafood provide heme iron. For mild deficiency or prevention, increasing dietary iron alongside vitamin C-rich foods can make a real difference. But for diagnosed anemia, food alone rarely provides enough iron to correct the deficit in a reasonable timeframe, and supplements are almost always needed.
Boosting and Blocking Absorption
Vitamin C significantly increases iron absorption, especially from plant sources and supplements. Even a small amount helps: roughly 20 mg of vitamin C (about what you’d get from a few strawberries) meaningfully improves absorption from a meal with moderate iron content. Taking your iron pill with a glass of orange juice or alongside vitamin C-rich foods is one of the simplest ways to get more from each dose.
On the other hand, several common foods and drinks interfere with iron absorption. Tea and coffee contain tannins that can reduce iron uptake by 60% to 90% when consumed with a meal. The effect varies depending on the amount and what else you’re eating, but the safest approach is to separate your iron supplement from tea or coffee by at least an hour or two. Calcium-rich foods and dairy may also compete with iron for absorption, so spacing your iron supplement away from meals heavy in cheese or milk is a reasonable precaution.
Dealing With Side Effects
Gastrointestinal problems are the most common reason people stop taking iron. Nausea, constipation, diarrhea, stomach pain, and a metallic taste are all typical. Your stools will also turn dark green or black, which is harmless but can be alarming if you’re not expecting it.
If side effects are making daily doses intolerable, a few adjustments can help. Taking iron with a small amount of food reduces stomach irritation, though it also slightly decreases absorption. Switching to every-other-day dosing, or even three times a week, lowers side effects while still allowing meaningful absorption. Some people also tolerate ferrous gluconate better than ferrous sulfate, since the lower elemental iron content per pill means less irritation per dose, even if you need to take more pills overall.
When Oral Iron Isn’t Enough
Some people genuinely cannot correct their anemia with pills. Intravenous iron bypasses the gut entirely and is the better option in several specific situations. People with inflammatory bowel disease often find that oral iron worsens their symptoms, because iron is irritating to the intestinal lining and promotes the growth of harmful gut bacteria. After certain bariatric surgeries, particularly Roux-en-Y gastric bypass, the part of the intestine that absorbs iron has been rerouted, making oral supplements essentially useless.
Heavy menstrual bleeding is another common scenario where oral iron simply can’t keep pace with ongoing losses. The same applies in the second and third trimesters of pregnancy, when iron demands spike. In chronic inflammatory conditions like heart failure or kidney disease, a protein called hepcidin blocks iron absorption in the gut, and IV iron can overcome that block where oral supplements cannot.
IV iron works faster, too. Hemoglobin typically starts rising within about a week of infusion, with meaningful increases by 10 to 16 days. For oral iron, the trajectory is much slower, and full store replenishment can take months. The trade-off is that IV iron requires a clinical visit and, rarely, can cause infusion reactions.
Figuring Out What Type You Have
A simple blood test can distinguish between iron deficiency, B12 deficiency, and other causes of anemia. Ferritin, the blood marker for iron stores, is the single most useful test. Levels below 30 μg/L reliably indicate iron deficiency. If you have a chronic inflammatory condition like rheumatoid arthritis or kidney disease, that threshold rises to 100 μg/L, because inflammation artificially inflates ferritin readings.
Hemoglobin levels determine whether your iron deficiency has progressed to actual anemia. The World Health Organization defines anemia as hemoglobin below 130 g/L in men, below 120 g/L in non-pregnant women, and below 110 g/L during pregnancy. You can be iron-deficient without being anemic yet, and treating at that earlier stage prevents symptoms from developing. Common signs of iron-deficiency anemia include fatigue, pale skin, shortness of breath with exertion, brittle nails, and cold hands and feet.