Iron Deficiency: Signs You Might Be Low

Iron is the mineral your body uses to build hemoglobin, the protein in red blood cells that carries oxygen around your body. When iron runs low, your tissues get less oxygen, and you start to feel it, often as a tiredness that sleep does not fix.

Iron deficiency is one of the most common nutrient shortfalls, and it can creep up slowly. This article explains the signs, who is most at risk, how it is tested and what usually helps. It can help you decide whether to ask for a blood test. It cannot tell you whether you are low; only testing can.

What is iron deficiency?

Iron deficiency is when your body's iron stores fall too low to meet its needs. It develops in stages: first your stored iron drops, then the iron available for making red blood cells runs short, and finally you may develop iron-deficiency anemia, which means you have fewer or smaller red blood cells than normal.

According to the NIH Office of Dietary Supplements (ODS), iron is also needed for growth, brain development, and making some hormones. That is why low iron can affect far more than energy. Iron sits alongside other nutrients covered in our guide to nutrition and wellness, where a varied diet is the foundation.

You can be low in iron without being anemic yet. That early stage often has mild or no symptoms, which is one reason people go a long time without realizing.

What are the signs of iron deficiency?

The most common sign of iron deficiency is fatigue: feeling tired, weak and short of energy even after rest. The National Heart, Lung, and Blood Institute (NHLBI) and MedlinePlus list a range of other signs that tend to appear as iron drops further.

• Tiredness and weakness
• Pale skin, or paleness inside the lower eyelids
• Shortness of breath, especially with activity
• Dizziness or lightheadedness
• Headaches
• Fast or irregular heartbeat
• Cold hands and feet
• Brittle nails, or nails that curve inward like a spoon
• A sore or swollen tongue
• Craving ice, clay, dirt or starch, a pattern called pica
• Restless legs, an urge to move your legs while resting

Many of these signs are vague, and each one has other possible causes. Cold hands and feet, for example, can come from circulation, thyroid problems or simply a cold room, as our article on why your hands and feet stay cold explains.

Why does iron deficiency make you so tired?

Iron deficiency makes you tired because your blood carries less oxygen. Every cell needs oxygen to make energy, so when supply drops, muscles tire faster, your brain feels foggy, and your heart and lungs work harder to compensate.

That tiredness is easy to blame on stress, poor sleep or a busy life. It is also only one of many causes of fatigue. If exhaustion is your main complaint, our article on reasons you feel tired all the time walks through the others worth ruling out.

Who is most likely to be low in iron?

Some groups are much more likely to run low on iron. ODS identifies these groups as being at higher risk:

• People who menstruate, especially those with heavy periods, because of regular blood loss
• Pregnant people, whose iron needs rise sharply to support the growing baby
• Infants and young children, particularly babies born early or at low birth weight
• Frequent blood donors
• People with cancer, heart failure, or digestive conditions such as celiac disease, ulcerative colitis or Crohn's disease, which can cause blood loss or reduce absorption
• People who have had weight-loss surgery that changes how food is absorbed
• Vegetarians and vegans, because iron from plants is absorbed less well

Blood loss you cannot see can also drain iron. Slow bleeding in the digestive tract, from an ulcer or, less often, a growth in the colon, may cause iron deficiency with no other obvious symptoms. That is why a doctor may look for a cause rather than just prescribing iron, especially in men and in women past menopause.

How much iron do you need?

How much iron you need depends on your age, sex and life stage. The Recommended Dietary Allowance (RDA), the daily amount that meets the needs of nearly all healthy people, is set by the National Academies and published by ODS.

ODS notes that vegetarians may need about 1.8 times these amounts, because the body absorbs nonheme iron (the form in plants) less efficiently than heme iron (the form in meat, poultry and seafood).

How is iron deficiency tested?

Iron deficiency is confirmed with blood tests, which your primary care provider can order. A complete blood count (CBC) shows your hemoglobin level and the size of your red blood cells, and iron studies show how much iron you have stored and circulating.

One common test is ferritin, a protein that stores iron; a low ferritin level is a strong sign your stores are depleted. Other tests may include serum iron, transferrin saturation and total iron-binding capacity. Your doctor reads these together, because inflammation and other conditions can push some results up or down.

Iron deficiency is not the only nutrient problem that causes anemia and fatigue. Low vitamin B12 can look similar, and our piece on signs of low vitamin B12 explains how it differs.

Which foods help raise your iron?

Food is the foundation for keeping iron levels healthy, though it may not be enough on its own to correct a real deficiency. Iron comes in two forms in food, and pairing them well can make a difference.

• Heme iron is found in red meat, poultry and seafood, such as beef, chicken, oysters, clams and sardines. It is absorbed more easily.
• Nonheme iron is found in beans, lentils, tofu, spinach, nuts, seeds and iron-fortified breakfast cereals and breads.

ODS notes that eating vitamin C rich foods, such as citrus, tomatoes, peppers or strawberries, at the same meal can help your body absorb nonheme iron. Meat, poultry and seafood in a meal also help. Tea and coffee with meals, and calcium supplements, may reduce absorption, so some people take them between meals instead.

For practical meal ideas, see our list of everyday foods rich in iron. A registered dietitian (RD or RDN) can also help you build a plan, especially if you eat a vegetarian or vegan diet.

Should you take an iron supplement?

Only take an iron supplement if a doctor has confirmed you are low or advised you to. Iron is one of the supplements where more is not better: too much can cause constipation, nausea and stomach pain, and very high doses can be dangerous.

The FDA requires a warning on iron-containing supplements because accidental overdose of iron products is a leading cause of fatal poisoning in children under 6. Keep any iron supplement locked away and out of children's reach. If a child swallows iron pills, call Poison Control at 1-800-222-1222 or 911 right away.

Some people also have hemochromatosis, an inherited condition that makes the body absorb and store too much iron. Taking iron without testing could harm them, which is another reason to check before you start. When iron is prescribed, your doctor will usually recheck your blood after a few months to see whether levels are rising and whether the cause has been found.

When should you see a doctor?

See your doctor if you have ongoing tiredness, pale skin, shortness of breath, cravings for ice, or several of the signs above for more than a couple of weeks. It is also worth asking about testing if you have heavy periods, are pregnant or planning pregnancy, eat a plant-based diet, or have a digestive condition.

Get medical help quickly if you notice:

• Black, tarry or bloody stools, or vomiting blood or material that looks like coffee grounds. These can signal bleeding in the digestive tract.
• Very heavy periods that soak through a pad or tampon every hour for several hours.
• Chest pain, fainting or severe shortness of breath. Call 911 or go to the emergency room.
• A child who may have swallowed iron tablets. Call Poison Control or 911 right away.

It helps to bring a short list to your appointment: how long you have felt this way, how heavy your periods are if you menstruate, what you usually eat in a day, any supplements or medicines you take, and whether anyone in your family has had anemia or hemochromatosis. That information helps your doctor decide which tests to order and where to look for a cause, and it makes the visit faster and more useful for you.

Iron deficiency is common and usually very treatable once it is found. The most useful step is not guessing but getting a simple blood test and finding out why your iron is low.