Iron deficiency is treated with oral supplements, dietary changes, or intravenous iron, depending on how depleted your stores are and what’s causing the loss. Most people start with oral iron tablets and can expect their blood counts to improve within two to four months, though fully restocking your body’s iron reserves takes longer.
How Iron Deficiency Is Diagnosed
The key blood test is ferritin, a protein that reflects how much iron your body has in storage. The World Health Organization has traditionally used a ferritin below 15 ng/mL as the cutoff for iron deficiency, but that threshold catches people only after their stores are essentially empty and many are already anemic. A growing body of evidence points to 50 ng/mL as a more accurate threshold. At that level, your gut has already started ramping up iron absorption and the hormonal signals regulating iron are shifting, both signs your body recognizes the shortage before a standard test might flag it.
In practice, many clinicians use a ferritin below 30 ng/mL as a working diagnosis of iron deficiency. If you have an inflammatory condition like kidney disease or rheumatoid arthritis, ferritin can appear falsely normal because inflammation pushes the number up. In those cases, doctors rely on additional markers like transferrin saturation to get the full picture.
Iron deficiency without anemia is common and underdiagnosed. Among females aged 12 to 21 in the U.S., nearly 40% had ferritin levels below 25 ng/mL. You don’t need to be anemic to feel the effects: fatigue, brain fog, restless legs, and hair thinning can all show up well before your hemoglobin drops.
Oral Iron Supplements
Oral iron is the first-line treatment for most people. Supplements come in several forms, and the important number is how much elemental iron (the actual usable iron) each one delivers. Ferrous fumarate is 33% elemental iron by weight, ferrous sulfate is 20%, and ferrous gluconate is 12%. A typical iron-only supplement provides about 65 mg of elemental iron per tablet. Your body absorbs only a fraction of that, and anything left unabsorbed sits in your gut, which is why side effects are so common.
At doses above 45 mg of elemental iron per day, nausea, constipation, and stomach discomfort become frequent complaints. If side effects are derailing your treatment, alternate-day dosing is worth trying. When you take iron, your body releases a hormone called hepcidin that stays elevated for roughly 24 hours and blocks further absorption. Taking your next dose the following day means you’re essentially competing against that hormonal brake. Spacing doses to every other day lets hepcidin drop back down, so your gut absorbs more iron from each tablet. A 2024 randomized trial found that women taking iron on alternate days had gastrointestinal side effects at a rate of just 9%, compared to 45% in the daily group, while actually achieving a greater increase in hemoglobin. A separate Swiss trial showed similar ferritin gains with fewer side effects and lower rates of iron deficiency returning over six months.
Take your supplement on an empty stomach if you can tolerate it, ideally in the morning. Pairing it with a source of vitamin C significantly boosts absorption of non-heme iron (the type found in supplements and plant foods). Vitamin C can even counteract the blocking effect of substances like tea, coffee, and calcium. On the flip side, avoid taking your iron tablet with dairy, coffee, tea, or calcium supplements, as these interfere with uptake.
What to Expect: The Treatment Timeline
If you’re anemic, your hemoglobin should rise noticeably within four weeks of starting supplementation. Full correction of anemia typically takes two to four months, assuming you’re taking the right dose and any underlying cause of the deficiency (heavy periods, a bleeding ulcer, poor absorption) is being addressed.
Here’s the part many people miss: once your hemoglobin normalizes, you are not done. Your body’s iron stores are still depleted. Continuing supplementation for an additional four to six months after anemia resolves is necessary to refill those reserves. Stopping too early is one of the most common reasons iron deficiency comes back. Total treatment time from start to full repletion can reach six months or more.
Iron-Rich Foods That Help
Diet alone rarely fixes a true deficiency, but the right foods accelerate recovery alongside supplements and help prevent recurrence. The type of iron in food matters enormously. Heme iron, found only in animal products, is absorbed at a rate of about 25%. Non-heme iron, found in plants and eggs, is absorbed at 17% or less.
The richest sources of heme iron include red meat, dark-meat poultry (thighs and drumsticks over breast meat), fish, and shellfish. Oysters and clams are particularly concentrated sources. For non-heme iron, the best options are lentils, chickpeas, dark leafy greens like spinach and kale, pumpkin seeds, quinoa, and dried apricots. Eggs contain non-heme iron despite being an animal product.
You can meaningfully improve absorption from plant-based meals by adding vitamin C. Squeeze lemon over your lentils, add bell peppers to a spinach salad, or eat strawberries alongside fortified cereal. The enhancement is directly proportional to the amount of vitamin C present, so more is genuinely better here. Conversely, drinking tea or coffee with an iron-rich meal can cut absorption substantially.
When IV Iron Is Needed
Intravenous iron bypasses the gut entirely, delivering iron straight into the bloodstream. It’s used when oral supplements aren’t working, aren’t tolerated, or can’t be absorbed properly. Several specific situations make IV iron the better choice:
- Inflammatory bowel disease. Conditions like Crohn’s disease and ulcerative colitis drive up hepcidin through chronic inflammation, which blocks iron absorption in the gut. Clinical guidelines for IBD actually recommend IV iron as the preferred route rather than a backup plan. Most anemic IBD patients have total iron deficits of 1,000 mg or more.
- Chronic kidney disease. Patients on dialysis or taking medications that stimulate red blood cell production often need IV iron because their bodies trap iron in storage rather than releasing it for use.
- Severe intolerance to oral iron. Some people experience intolerable nausea, cramping, or constipation even with alternate-day dosing and lower doses. Switching to IV iron sidesteps these gut-related problems entirely.
- Inadequate response after a fair trial. If your ferritin and hemoglobin haven’t budged after several weeks of consistent oral supplementation, the issue may be absorption rather than compliance.
IV iron infusions are typically given in an outpatient clinic and take 15 minutes to an hour depending on the formulation. Some people need a single session, while others require two or more spaced a few weeks apart. Side effects are generally mild, most commonly a temporary headache or metallic taste, though allergic reactions are possible and the reason infusions are given in a medical setting.
Why Finding the Underlying Cause Matters
Replacing iron without figuring out why you’re losing it is like bailing water without plugging the hole. In premenopausal women, heavy menstrual bleeding is the most common driver. In men and postmenopausal women, the cause is more likely gastrointestinal: ulcers, polyps, celiac disease, or even regular use of anti-inflammatory painkillers that cause slow bleeding in the stomach lining. Endurance athletes lose iron through foot-strike damage to red blood cells, sweat, and minor GI bleeding during intense training. Frequent blood donors are another group that quietly depletes their stores over time.
If your iron deficiency is unexplained or keeps returning despite adequate supplementation, expect your doctor to investigate further with stool tests, celiac screening, or a referral for endoscopy. Treating the root cause is what makes the difference between a one-time correction and a cycle of depletion and repletion that stretches on for years.