Can Iron Supplements Make You Gain Weight?

The most common nutrient deficiency in the United States, iron deficiency is typically found in women due to menstruation and childbearing. The symptoms of iron deficiency include fatigue, restless legs, pale skin, brittle nails, inflamed or sore tongue, cold hands and feet, and headaches and lightheadedness. Although it's not widely reported, weight gain may be a side effect of iron supplementation for some people. However, it's more likely that the iron deficiency itself is causing your weight gain.

There's scant scientific research to support claims that weight gain is linked to iron supplements. (Image: stockvisual/E+/GettyImages)

Iron Pills and Weight Gain

Neither WebMD nor Mayo Clinic links iron tablets and weight gain. It's not even listed as a rare side effect. However, there are anecdotal reports of women who claim their iron supplements have caused weight gain. But there's scant scientific research to support these claims.

One small study in the Egyptian Journal of Haematology in 2016 reported that there's a common connection between iron pills and weight gain. Thirty-three patients were observed for three months, during which time 30 patients gained weight. In the three who did not gain weight, no increase in hemoglobin — the iron-rich protein that carries oxygen in the blood — was observed. The rest of the patients gained weight, and the amount of weight gained was associated with the level of increase in hemoglobin.

Side Effects of Iron Deficiency

Weight gain is more likely to be a side effect of the iron deficiency itself than the supplement used to treat it. Sufficient iron is needed to activate thyroid hormones involved in metabolism. Low levels of thyroid hormone due to iron deficiency — or another reason — can cause stubborn weight gain that may persist until your blood levels are back to normal.

Some of the side effects of iron deficiency could also make it hard for you to maintain your weight. Fatigue, weakness and lightheadedness can make it difficult to exercise, which is a crucial component of managing your weight. It can also make it harder to prepare healthy meals and avoid food cravings, since fatigue increases cravings, according to Pittsburgh-based functional medicine practitioner Dr. Will Cole. If you noticed weight gain before beginning supplementation and you continue to gain weight, observe your symptoms. If you're still feeling fatigue and weakness, then your iron blood levels may not be high enough yet.

Managing Side Effects

If you believe your iron supplements are causing your weight gain, make an appointment with your doctor. He can help you discover and resolve the real cause of your weight gain.

As your blood levels start returning to normal, you'll begin to feel better. You may have more energy to exercise and prepare healthy foods at each meal. Along with treating a potential underlying cause of your weight gain, a healthy calorie-controlled diet and regular exercise is the best way to prevent weight gain and lose weight.

The Centers for Disease Control and Prevention recommends getting at least 150 minutes of moderate-intensity exercise each week, such as brisk walking, jogging or swimming. The CDC also recommends doing strength-training activity two days a week to build muscle, which will help you burn body fat. Limit your diet to primarily whole foods, including fresh fruits and vegetables, lean protein, whole grains, low-fat dairy, healthy oils — such as olive oil — and nuts and seeds. These nutrient-rich foods can help you lose weight and help you keep your vitamin and mineral levels in check.

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