If you have low iron, the most important steps are confirming it with a blood test, identifying why it’s low, and starting to rebuild your stores through diet changes, supplements, or both. Most people see noticeable improvement in energy and symptoms within a few weeks of treatment, but fully restoring your iron reserves takes several months.
Get a Blood Test to Confirm
Symptoms like fatigue, brain fog, pale skin, and feeling cold can suggest low iron, but they overlap with dozens of other conditions. A blood test is the only way to know for sure. The key marker is ferritin, a protein that reflects how much iron your body has stored. A ferritin level below 15 µg/L is diagnostic of iron deficiency. Levels between 15 and 30 are considered probable deficiency. Above 100 generally means your stores are in good shape.
Your doctor will also check your hemoglobin to see whether low iron has progressed to anemia, meaning your blood can no longer carry oxygen efficiently. Iron deficiency and iron deficiency anemia are related but not the same thing. You can be iron deficient with normal hemoglobin, which means you’re depleted but your body is still compensating. Either way, treatment is worth pursuing because low stores will eventually catch up with you.
Figure Out Why Your Iron Is Low
Low iron is always a symptom of something else. Rebuilding your stores without addressing the underlying cause means they’ll just drop again. The most common reasons fall into a few categories:
- Heavy periods. This is the leading cause in premenopausal women. If you soak through a pad or tampon every hour or two, or your period lasts more than seven days, the blood loss can outpace what your diet replaces.
- Not enough iron in your diet. Vegetarians, vegans, and people who eat very little red meat are at higher risk simply because the most absorbable form of iron comes from animal foods.
- Poor absorption. Celiac disease, inflammatory bowel disease, and prior stomach or intestinal surgery can all prevent your gut from taking in iron properly, even if you eat plenty of it.
- Internal bleeding. Peptic ulcers, colon polyps, and colorectal cancer can cause slow, invisible blood loss. Regular use of over-the-counter pain relievers like aspirin, ibuprofen, and naproxen can also cause internal bleeding over time.
- Pregnancy. Your blood volume increases dramatically, and the growing baby draws heavily on your iron reserves. Without supplementation, iron deficiency during pregnancy is very common.
If your doctor can’t identify an obvious dietary or menstrual cause, they may recommend further testing to rule out gut conditions or hidden bleeding. This is especially important for men and postmenopausal women, where iron deficiency is less expected and more likely to signal something that needs attention.
Eat More Iron-Rich Foods
Your body absorbs iron from animal sources (called heme iron) much more efficiently than iron from plants (non-heme iron). If you eat meat, the richest sources per serving are oysters (6.9 mg in just three oysters), mussels (5.7 mg per three ounces), and beef or bison (around 2.5 to 2.9 mg per three ounces). Sardines, crab, lamb, and turkey leg all contribute meaningful amounts too.
Plant-based sources can still make a real difference, especially fortified foods. A half cup of fortified whole-grain cereal packs over 16 mg of iron. One cup of cooked spinach provides 6.4 mg. Cooked soybeans, lima beans, and lentils are strong options, and even cashews and sesame seeds contribute a couple of milligrams per serving. The trick with plant iron is pairing it with vitamin C, which significantly boosts absorption. Think tomato sauce on lentils, bell peppers in a bean stir-fry, or a glass of orange juice with your morning cereal.
At the same time, be aware of what blocks absorption. Tea, coffee, and wine contain tannins that bind to iron and carry it out of your body. Calcium and dairy reduce absorption of plant-based iron. Bran and other high-fiber whole grains contain compounds called phytates that do the same. None of these foods are bad for you, but if you’re trying to maximize iron intake, avoid consuming them at the same meal as your iron-rich foods.
Consider an Iron Supplement
Diet alone is often enough to prevent deficiency but not always enough to correct one that’s already established. If your ferritin is truly low, your doctor will likely recommend a supplement. The standard treatment dose for iron deficiency anemia is about 120 mg of elemental iron per day for three months. That’s “elemental” iron, which is the actual amount of iron in the pill. A common 325 mg ferrous sulfate tablet, for example, contains only 65 mg of elemental iron.
Iron supplements are best absorbed on an empty stomach. Taking them with a small amount of vitamin C (even just a few sips of orange juice) improves uptake. Avoid taking them with coffee, tea, dairy, or calcium supplements.
Reducing Side Effects
Stomach cramps, nausea, and constipation are the most common complaints with iron supplements, and they cause a lot of people to stop taking them. One well-supported strategy is alternate-day dosing. A randomized trial published in The Lancet’s eClinicalMedicine tested this in 150 iron-depleted women taking 100 mg of iron. The group that took iron every other day had significantly fewer gastrointestinal side effects compared to those who took it daily. After six months, the alternate-day group actually had lower rates of iron deficiency (3% vs. 11.4%), likely because their bodies absorbed each dose more efficiently.
The science behind this involves hepcidin, a hormone that regulates iron absorption. After you take a dose of iron, hepcidin spikes and stays elevated for about 24 hours, which temporarily blocks your gut from absorbing the next dose efficiently. By 48 hours, hepcidin returns to baseline. So taking iron every other day means each dose hits your system when it’s most receptive. If daily dosing is making you miserable, ask your doctor about switching to this approach.
When IV Iron Makes More Sense
Oral supplements work for most people, but in certain situations, iron delivered directly into a vein is more appropriate. IV iron is considered when oral supplements haven’t worked after a reasonable trial, when you can’t tolerate them due to side effects, or when your body simply can’t absorb oral iron well (as with inflammatory bowel disease, celiac disease, or after bariatric surgery). It’s also used when iron needs to be restored quickly, such as before a surgery scheduled within six weeks, or when anemia is severe and causing significant symptoms.
For people with chronic kidney disease or those undergoing chemotherapy, IV iron is often the recommended first-line treatment rather than a backup option. The procedure itself is straightforward: an infusion at a clinic that typically takes 15 to 60 minutes depending on the formulation. Some people need just one session, others need a short series.
How Long Recovery Takes
Once you start treatment, symptoms like fatigue and brain fog often begin improving within the first one to two weeks. Hemoglobin levels typically start rising within two to four weeks and should normalize within two to three months of consistent supplementation.
But here’s what many people don’t realize: normal hemoglobin does not mean you’re done. Hemoglobin recovers first because your body prioritizes making red blood cells. Your deeper iron reserves, reflected by ferritin, take much longer to rebuild. Most guidelines recommend continuing iron supplementation for at least three months after your hemoglobin normalizes, specifically to refill those stores. Stopping too early is one of the most common reasons iron deficiency comes back. Your target is a ferritin level above 100 µg/L, which indicates genuinely healthy reserves, not just the bare minimum.
Follow-up blood work is important. A recheck around four to six weeks after starting treatment confirms you’re responding, and another test after you’ve completed the full course confirms your stores are actually replenished.