If you have low iron, the most important steps are figuring out why your levels dropped, increasing your iron intake through food or supplements, and making sure your body actually absorbs what you’re taking in. Low iron is one of the most common nutritional deficiencies worldwide, and it can leave you exhausted, short of breath, and foggy-headed. The good news: it’s very treatable once you approach it the right way.
Know What Your Numbers Mean
Iron deficiency and iron deficiency anemia are related but not identical. You can have depleted iron stores without being anemic yet. The key blood marker is ferritin, a protein that reflects how much iron your body has in reserve. A ferritin level below 30 ng/mL means iron deficiency, whether or not you feel symptoms.
Anemia develops when iron drops low enough that your body can’t make enough healthy red blood cells. The World Health Organization defines anemia as hemoglobin below 13 g/dL in men and below 12 g/dL in women. If your doctor has told you that you have low iron, ask which category you fall into, because the urgency and treatment approach differ. Another useful marker is transferrin saturation: a result below 20% signals that not enough iron is being transported through your blood.
Figure Out Why Your Iron Is Low
Taking supplements without understanding the cause is like mopping the floor while the faucet is still running. The most common reasons iron drops fall into three categories: losing blood, not absorbing iron well, or not getting enough from your diet.
Heavy menstrual periods are the leading cause in premenopausal women. Slow, invisible blood loss inside the body is another major culprit, often from peptic ulcers, colon polyps, or even regular use of over-the-counter pain relievers like ibuprofen or aspirin. Colorectal cancer can also cause this kind of hidden bleeding, which is why doctors sometimes recommend further investigation when iron deficiency shows up unexpectedly, especially in men or postmenopausal women.
Absorption problems are surprisingly common. Celiac disease, Crohn’s disease, ulcerative colitis, and previous surgery on the small intestine can all prevent your gut from pulling iron out of food efficiently. Pregnancy increases iron demands significantly, and frequent blood donors are also at higher risk. If your iron keeps dropping despite eating well, one of these underlying causes is likely at play.
Eat More Iron-Rich Foods
Not all dietary iron is created equal. Iron in food comes in two forms: heme iron from animal sources and non-heme iron from plants. Your body absorbs about 25% of heme iron but 17% or less of non-heme iron. That gap matters when you’re trying to rebuild your stores.
The best heme iron sources are red meat, poultry (especially dark meat like thighs and drumsticks), fish, and shellfish. For non-heme iron, focus on beans, lentils, dark leafy greens like spinach, nuts, seeds, whole grains, fortified cereals, dried fruits, and dark chocolate. Pairing non-heme iron foods with vitamin C (think: spinach salad with bell peppers, or oatmeal with strawberries) significantly boosts absorption.
Dietary changes alone can maintain healthy iron levels, but if you’re already deficient, food usually isn’t enough to catch up quickly. That’s where supplements come in.
Choose the Right Supplement
Iron supplements can be confusing because the dose on the label isn’t the amount of iron your body actually gets. What matters is “elemental iron,” the portion your body can use. Different supplement forms contain very different amounts:
- Ferrous sulfate (dried) contains 37% elemental iron, so a 325 mg tablet delivers about 120 mg of actual iron.
- Ferrous fumarate contains 33% elemental iron, giving you roughly 99 mg per 300 mg tablet.
- Ferrous gluconate contains only 12% elemental iron, delivering about 39 mg per 325 mg tablet.
Ferrous sulfate is the most commonly prescribed because it packs the most iron per tablet. Ferrous gluconate is gentler on the stomach but delivers far less iron per dose. Iron bisglycinate, a chelated form, is another option that some people tolerate better, though it’s typically more expensive. If one form gives you stomach trouble (nausea, constipation, or cramping are common complaints), switching to a different form often helps.
Time Your Supplement for Better Absorption
How and when you take iron matters almost as much as what you take. Iron absorbs best on an empty stomach, ideally 30 to 60 minutes before eating. Taking it with a small glass of orange juice or another vitamin C source can boost absorption further.
Certain foods and drinks actively block iron absorption. Coffee is one of the worst offenders: drinking it with a meal or within an hour after eating can significantly reduce how much iron you absorb. Interestingly, coffee consumed an hour before a meal doesn’t seem to have the same effect. Tea contains similar compounds that interfere with absorption. Calcium, whether from dairy products or supplements, also competes with iron. The simplest strategy is to take your iron supplement on its own, away from meals, coffee, tea, and calcium by at least one to two hours.
Consider Every-Other-Day Dosing
A counterintuitive finding has changed how many clinicians recommend iron supplements. Taking iron every other day may work nearly as well as taking it daily. In a randomized controlled trial of 200 adults with iron deficiency anemia, those who took 120 mg of elemental iron every other day saw their hemoglobin rise by an average of 1.05 g/dL over eight weeks, compared to 1.36 g/dL in the daily group. That difference was not statistically significant.
The logic behind this approach involves a hormone called hepcidin. When you take a dose of iron, your body temporarily raises hepcidin levels, which blocks further iron absorption for roughly 24 hours. By skipping a day, you may be taking your next dose when absorption is at its peak. Every-other-day dosing can also reduce side effects like nausea and constipation, making it easier to stick with treatment long-term.
When Oral Supplements Aren’t Enough
Some people don’t respond well to oral iron. If you have inflammatory bowel disease, chronic kidney disease, have had bariatric surgery, or simply can’t tolerate pills, intravenous iron may be a better option. IV iron bypasses the gut entirely and delivers iron directly into the bloodstream.
IV iron is also used when speed matters, such as preparing for surgery within a few weeks or treating severe symptomatic anemia. For surgeries with six or more weeks of lead time, oral supplements are usually sufficient. With less time, IV iron is the preferred route. The infusion itself typically takes 15 to 60 minutes depending on the product, and many people notice improved energy within a week or two.
How Long Recovery Takes
Rebuilding iron stores is a slow process. Even with consistent supplementation, it can take up to six months to fully replenish your reserves. If you started with anemia, your hemoglobin will typically begin rising within a few weeks, but the recommendation is to continue iron therapy for an additional four to six months after your hemoglobin normalizes. This extended phase is what actually refills your body’s deeper iron stores.
Your doctor will likely recheck your ferritin three to six months after starting treatment. Many people make the mistake of stopping supplements as soon as they feel better, which is usually well before their stores have recovered. Stopping too early is one of the most common reasons iron deficiency comes back.
If your ferritin and hemoglobin haven’t improved after two to three months of oral supplementation, that’s a signal something else is going on. Poor absorption, ongoing blood loss, or an incorrect diagnosis could all be factors worth investigating further.