Treating low ferritin typically involves oral iron supplements taken over three to six months, combined with dietary changes that boost iron intake and absorption. The specific approach depends on how low your levels are and what’s driving the deficiency. A ferritin level below 30 mcg/L indicates iron deficiency, while a level below 10 mcg/L suggests you’ve progressed to iron deficiency anemia.
Why Ferritin Dropped in the First Place
Ferritin is a protein that stores iron, so a low reading means your body’s iron reserves are depleted. Before jumping straight to supplements, it helps to understand what caused the drop, because treatment works best when you address the root cause alongside replenishing stores.
The most common reasons for low ferritin are blood loss, poor absorption, and insufficient dietary intake. Heavy menstrual periods are the single biggest driver in premenopausal women. Gastrointestinal conditions like Crohn’s disease, ulcerative colitis, and acid reflux can cause slow, chronic blood loss that drains iron stores over months. Celiac disease and prior weight loss surgery interfere with your gut’s ability to absorb iron from food. And some people simply aren’t eating enough iron-rich foods to keep up with their body’s demand.
A sudden, unexplained drop in ferritin can sometimes point to stomach ulcers, colon polyps, or in rarer cases gastrointestinal cancer. If your doctor can’t identify an obvious cause, they may recommend further investigation.
Oral Iron Supplements
Oral iron is the standard first-line treatment. Supplements come in several forms, and the key number to look for on the label is “elemental iron,” which tells you how much actual iron your body gets per dose. Different formulations contain different amounts: ferrous fumarate is about 33% elemental iron by weight, ferrous sulfate is 20%, and ferrous gluconate is 12%. You don’t need to do the math yourself since the Supplement Facts panel lists elemental iron directly.
Ferrous forms (ferrous sulfate, ferrous fumarate, ferrous gluconate) are more readily absorbed than ferric forms. However, they’re also more likely to cause side effects like nausea, constipation, and a metallic taste. Chelated forms, such as iron bisglycinate, heme iron polypeptides, and polysaccharide-iron complexes, tend to be gentler on the stomach, though they often cost more.
Doses above 45 mg of elemental iron per day are where gastrointestinal side effects become common. Your doctor may prescribe higher doses if your deficiency is severe, but for many people, a moderate dose taken consistently over months works just as well with fewer problems.
Alternate-Day Dosing Reduces Side Effects
If iron supplements upset your stomach, taking them every other day instead of daily can make a real difference. A randomized, double-blind study published in The Lancet’s eClinicalMedicine compared alternate-day and consecutive-day dosing in iron-depleted women, giving both groups the same total amount of iron. After three months, ferritin levels were virtually identical between the two groups (around 44 mcg/L each). But the alternate-day group reported significantly fewer gastrointestinal side effects.
Even more striking, at six months the alternate-day group had a lower rate of iron deficiency (3% versus 11%), likely because fewer side effects meant better long-term compliance. People who can actually tolerate their supplements keep taking them. If daily dosing is making you miserable, switching to every other day is a well-supported alternative.
How to Maximize Absorption
What you eat and drink around your iron supplement matters as much as the supplement itself. A few simple timing strategies can significantly improve how much iron your body actually absorbs.
- Take iron with vitamin C. Vitamin C helps your small intestine absorb non-heme iron (the type in supplements and plant foods). A glass of orange juice or a few strawberries alongside your supplement is enough.
- Separate iron from calcium. Calcium interferes with iron absorption. Space calcium-rich foods and calcium supplements at least one to two hours away from your iron dose. This includes milk, yogurt, cheese, and calcium-fortified beverages.
- Avoid tea, coffee, and wine at meal time. These contain tannins, compounds that bind to iron and reduce uptake. Spacing them an hour or two from your iron-rich meal or supplement helps.
- Take supplements on an empty stomach if tolerable. Iron absorbs best between meals. If that causes nausea, taking it with a small amount of food is a reasonable trade-off.
Iron-Rich Foods That Help
Dietary changes alone rarely fix a true deficiency, but they support supplementation and help maintain healthy levels once you’ve recovered. The difference in absorption between animal and plant sources is dramatic: heme iron from meat, poultry, and seafood is absorbed at a rate of 25 to 30%, while non-heme iron from plants is absorbed at roughly 3 to 5%.
Red meat, liver, oysters, and dark-meat poultry are the most efficient dietary sources. For plant-based eaters, lentils, chickpeas, tofu, spinach, and fortified cereals provide non-heme iron, but you’ll need to pair them with vitamin C and avoid calcium and tannins at the same meal to get meaningful absorption. Cooking in cast iron can also add small amounts of iron to food, particularly with acidic dishes like tomato sauce.
How Long Treatment Takes
Rebuilding iron stores is slow. If your ferritin is low but your hemoglobin is still in the normal range, expect to supplement for three to six months. You should see hemoglobin start to rise within two to three weeks if anemia is present, which is a good early sign that treatment is working. Ferritin takes longer to climb because your body prioritizes making red blood cells before it starts filling storage reserves.
Many people feel better within a few weeks, particularly if they had symptoms like fatigue, brain fog, or hair shedding. But stopping treatment too early is one of the most common mistakes. Even after symptoms improve, your stores need several more months to reach a level that prevents relapse.
When to Recheck Your Levels
Retesting too soon can give misleading results. General guidelines suggest rechecking ferritin and a complete blood count about two to three months after starting oral iron if your hemoglobin was above 100 g/L. If your hemoglobin was lower, your doctor may retest at one month to make sure you’re responding.
If you received intravenous iron, ferritin should not be rechecked within four weeks because the result will be artificially high. Peak ferritin after an IV infusion occurs around seven to nine days, then gradually settles to a more accurate reading. For people who remain symptomatic after initial treatment, retesting every three to six months helps guide next steps.
When Oral Iron Isn’t Enough
Some people don’t respond well to oral supplements. If you have a malabsorption condition like celiac disease, inflammatory bowel disease, or a history of gastric bypass surgery, your gut may not absorb oral iron efficiently regardless of dose or timing. Persistent heavy menstrual bleeding can also outpace what oral supplements can replenish.
In these cases, intravenous iron is typically the next option. IV iron bypasses the gut entirely and replenishes stores much faster, with ferritin levels peaking within about a week. It’s given as an infusion in a clinic or hospital, usually in one or two sessions. Side effects are generally mild, though allergic reactions are possible and the infusion is monitored for that reason. Your doctor may also investigate whether the underlying cause of iron loss, such as uncontrolled bleeding or undiagnosed celiac disease, needs its own treatment.