The most effective way to increase your hemoglobin is to address whatever’s causing it to be low, which usually means getting more iron, vitamin B12, or folate through food or supplements. Normal hemoglobin ranges from 13.2 to 16.6 g/dL for men and 11.6 to 15 g/dL for women. If your levels fall below those thresholds, dietary changes can often bring them back up within a few weeks, though the specific approach depends on the underlying cause.
Why Your Hemoglobin Might Be Low
Iron deficiency is the most common reason, but it’s not the only one. Hemoglobin drops through three basic mechanisms: blood loss, reduced red blood cell production, or faster-than-normal red blood cell destruction. Heavy menstrual periods, ulcers, and colon polyps can all cause slow, steady blood loss that drains your iron over time. Pregnancy increases your blood volume and iron demands simultaneously, making deficiency almost expected without supplementation.
Some causes have nothing to do with diet. Chronic kidney disease reduces production of the hormone that signals your bone marrow to make red blood cells. Chronic inflammatory conditions can trap iron inside cells, keeping it unavailable for hemoglobin production. Inherited blood disorders like sickle cell disease and thalassemia affect hemoglobin structure or red blood cell lifespan. If your hemoglobin stays low despite eating well and supplementing, one of these non-nutritional causes is worth investigating.
Iron: The Most Important Nutrient
Iron sits at the center of every hemoglobin molecule. Without enough of it, your body simply cannot build functional hemoglobin regardless of what else you eat. The iron in food comes in two forms, and the difference between them matters more than most people realize.
Heme iron, found only in animal foods, is absorbed far more efficiently than non-heme iron from plants. The richest heme sources include oysters, clams, mussels, beef and chicken liver, sardines, beef, and poultry. Non-heme iron comes from fortified cereals, beans, lentils, dark chocolate (at least 45% cacao), spinach, potatoes with skin, nuts, and seeds. Both forms contribute to your iron intake, but if you’re trying to raise low hemoglobin quickly, heme iron gives you more absorption per serving.
How to Get More From the Iron You Eat
Absorption of non-heme iron is surprisingly easy to manipulate. Eating vitamin C alongside iron-rich foods significantly boosts uptake. This can be as simple as squeezing lemon over lentils, eating strawberries with your fortified cereal, or having bell peppers with a bean dish. Heme iron eaten at the same meal also helps your body absorb more non-heme iron, so combining a small amount of meat with plant-based iron sources gives you a compounding benefit.
What you avoid eating with iron matters just as much. Polyphenols in tea reduced iron absorption from fortified bread by 56 to 72% in one study, and in women with iron deficiency anemia, tea cut absorption by more than 85%. Calcium decreases iron absorption by roughly 18 to 27%, with one study showing it cut absorption from 10.2% down to 4.8% from a single meal. The practical takeaway: drink your tea or coffee between meals rather than with them, and if you take a calcium supplement, separate it from your iron-rich meals or iron supplement by at least a couple of hours.
Vitamin B12 and Folate
Iron builds hemoglobin, but B12 and folate are essential for building the red blood cells that carry it. Without enough of either, your bone marrow produces fewer red blood cells, and the ones it does make are often oversized and inefficient. B12 deficiency is particularly common in people over 50, vegans, and anyone with digestive conditions that impair absorption. Good sources include meat, fish, eggs, and dairy, or a supplement if you eat little or no animal food.
Folate comes from leafy greens, legumes, citrus, and fortified grains. B12 and folate metabolism are intertwined in complex ways. B12 deficiency impairs your body’s ability to use folate effectively, so even if your folate intake is adequate, a B12 shortage can create a functional folate deficit. This is why correcting a low hemoglobin sometimes requires addressing both nutrients together.
Iron Supplements: What to Expect
When diet alone isn’t enough, oral iron supplements are the standard first step. Therapeutic doses typically range from 100 to 200 mg of elemental iron per day, depending on how low your levels are and how well you tolerate the supplement. For context, the tolerable upper intake for healthy adults who aren’t being treated for deficiency is 45 mg per day, so therapeutic doses are deliberately higher than what you’d get from food alone. Your doctor may prescribe above that threshold specifically because your stores need aggressive replenishment.
Side effects are common and dose-dependent: nausea, constipation, diarrhea, stomach discomfort, and dark-colored stools. The GI symptoms tend to fade as your body adjusts, though dark stools persist for the duration of treatment. If side effects are intolerable, taking supplements every other day instead of daily can reduce symptoms while still improving iron status, a strategy that research has increasingly supported.
How Long It Takes to See Results
Hemoglobin typically starts rising within 2 to 4 weeks of beginning iron replacement. That’s fast enough to notice improvements in energy and breathing, which is encouraging. But here’s what catches many people off guard: once your hemoglobin reaches a normal level, you’re not done. Your body’s deeper iron reserves, stored in the liver, spleen, and bone marrow, are still depleted. Continuing iron therapy for an additional 6 months after hemoglobin normalizes is generally recommended to fully replenish those stores and prevent a quick relapse.
Stopping too early is one of the most common reasons people end up with recurring low hemoglobin. The number on your blood test improves before the underlying deficit is resolved.
Exercise and Altitude
Aerobic exercise stimulates red blood cell production over time, though the effect is modest compared to fixing a nutritional deficiency. The more potent natural stimulus is altitude. When you spend time at high elevations, lower oxygen levels trigger your body to produce more red blood cells and hemoglobin to compensate. Research on workers with long-term intermittent altitude exposure showed hemoglobin increased by about 0.05 g/dL per year of exposure, a real but gradual effect.
For altitude to meaningfully boost red blood cell production, the elevation generally needs to exceed 4,000 meters (about 13,000 feet), and exposure needs to last at least two weeks. The response also depends on your starting red blood cell volume: people with lower baseline levels tend to see a larger increase. For most people, altitude training is impractical as a hemoglobin strategy, but it explains why athletes sometimes train at elevation before competitions.
Putting It All Together
If your hemoglobin is mildly low and you have no underlying medical condition, a focused dietary approach works well. Prioritize iron-rich foods, pair them with vitamin C, separate them from tea, coffee, and calcium, and make sure you’re getting adequate B12 and folate. If your levels are significantly below normal or you have symptoms like persistent fatigue, shortness of breath, or dizziness, supplementation under medical guidance will get you there faster. The 2 to 4 week mark is when you can expect to see your numbers start climbing, with full recovery of iron stores taking closer to 6 months of consistent effort.