Should I take an iron supplement? Here’s what the science says.
I’ve heard that iron supplements may ease fatigue. Should I start taking one?
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If you have iron-deficiency anemia, you should take an iron supplement. But here’s an interesting pro-tip I share with my patients: Don’t take it every day. A study found that taking an iron supplement every other day can optimize iron absorption - and may mitigate side effects such as nausea and constipation.
Iron is an essential micronutrient that helps produce healthy red blood cells. People with an iron deficiency often feel exhausted. Some may find it hard to catch their breath or notice paler skin (though this may be less obvious among those with black or brown skin tones). Iron deficiency can also lead to a racing heart, headaches and odd cravings, such as for ice, chalk or clay.
It’s normal to lose a small amount of the body’s iron stores through the skin or during menses. But you can develop a health problem called iron-deficiency anemia (one of several forms of anemia) if you lose more than you’re absorbing through your diet. Iron-deficiency anemia is a condition in which red blood cells aren’t able to carry oxygen efficiently to the rest of the body. It is characterized by both low levels of iron and red blood cells and diagnosed with blood tests, including a complete blood count and an iron panel.
Young children, people who have heavy menses or are pregnant, and older people should be particularly vigilant. A study published in the Annals of Internal Medicine last year found that about 1 in 4 healthy adults, age 70 and older, developed anemia within five years of enrolling in the study and that taking a low-dose daily aspirin increased that risk by 20 percent.
If you are feeling tired all the time, but have not been diagnosed with iron-deficiency anemia, work with your physician to investigate other possible causes.
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What causes low iron levels?
Pregnancy: During pregnancy, iron requirements multiply to support the mother and growing fetus (as if pregnant people needed another reason to feel exhausted), and so we screen for it routinely. Taking an iron supplement is safe during pregnancy and while breastfeeding.
Blood loss: Heavy bleeding during menses or from the gastrointestinal tract (which may not always be noticeable in your stool) both lead to iron depletion. Unexplained iron-deficiency anemia is a common reason to get a colonoscopy (and often also an upper endoscopy) because we don’t want to miss an important cause such as cancer.
Issues with iron absorption: Certain medical conditions make it hard to absorb iron from our gut - for instance, post-bariatric surgery, celiac disease, inflammatory bowel disease or gastritis (which becomes more common as we age). Depending on the condition, people may need intravenous iron instead of an oral supplement.
Iron-poor diet: Certain plants such as spinach or legumes are high in iron. However, our bodies absorb the iron contained in meat and fish much more efficiently. People on plant-based diets may be at a higher risk of iron deficiency, but that’s usually mitigated in countries like the United States, where foods such as cereals and flour are generally fortified with iron.
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The right way to take an iron supplement
Here are some ways to make iron supplements more effective:
Take it on an empty stomach: Ingesting the supplement an hour before eating or two hours after eating will help maximize absorption.
Swallow it with a glass of orange juice - and skip the milk and coffee: Vitamin C has been shown to promote iron absorption by creating a more acidic environment that helps iron dissolve. A 2020 randomized-controlled trial found that vitamin C supplementation in pill form did not improve iron absorption, but getting a healthy amount of vitamin C in your diet, such as through orange juice, could boost iron absorption fourfold. On the other hand, calcium-containing foods and beverages, including milk and yogurt, and polyphenol-containing drinks such as tea and coffee - can all decrease iron absorption. It’s okay to consume these at other times in the day - but avoid them around the same time as you take your iron supplement.
Help yourself to a stool softener: Constipation is a big reason people stop taking iron, so get on top of it before things back up! I usually tell my patients to preemptively take a stool softener (I typically start with psyllium) for the duration that they’re on iron supplements.
Rethink your antacid: Antacids such as omeprazole can interfere with iron absorption because they decrease acidity. Many people are on medications such as omeprazole for longer than they really need to be, so ask your physician if your daily antacid still makes sense and whether you can try coming down on the dose - or perhaps off it entirely.
Avoid “enteric-coated” capsules: These formulations - which apply a special coating meant to avoid degradation early in the digestive tract - sound good in theory, but because iron is absorbed by the first parts of the small intestine, “enteric-coated” tablets can bypass that key area of your gut so you won’t absorb as much as you should.
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What I want my patients to know
Iron-deficiency anemia can occur slowly - often over several months - so it can be hard to pinpoint exactly when you started to feel differently. And some of my female patients with heavy menses have normalized feeling fatigued, telling themselves “they’re just out of shape.”
Iron-deficiency anemia can be resolved (usually fairly easily), but we need to investigate its cause and treat it, if we can. Otherwise, people with long-term iron deficiency are at risk of heart problems and infections.
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