Iron Deficiency Anemia

What iron deficiency anemia is

Your body uses iron mainly to make hemoglobin, the red pigment in red blood cells that carries oxygen from the lungs to every tissue. About two thirds of the body's iron is in hemoglobin. The rest is stored, mainly as ferritin in the liver, spleen and bone marrow.

Iron deficiency develops in stages:

1. Iron depletion: stores run down, but hemoglobin is still normal. Ferritin is low.
2. Iron deficiency without anemia: the marrow struggles to make hemoglobin. Some people already feel tired.
3. Iron deficiency anemia: hemoglobin falls below normal. Red cells become small (microcytic) and pale (hypochromic).

Anemia generally means hemoglobin below about 13 g/dL in men, 12 g/dL in non-pregnant women and 11 g/dL in pregnancy. See anemia for other types.

Symptoms of iron deficiency anemia

Symptoms develop slowly, so many people get used to them and only realize how unwell they were after treatment.

Common symptoms:

• fatigue, low energy and poor exercise tolerance
• weakness
• pale skin, pale inner eyelids and pale gums
• shortness of breath with activity
• a fast or pounding heartbeat
• headaches, dizziness and lightheadedness
• cold hands and feet
• poor concentration

Signs more specific to iron deficiency:

• Pica: cravings for non-food items, especially ice (pagophagia), clay or starch
• brittle nails or spoon-shaped nails (koilonychia)
• a sore, smooth, red tongue and cracks at the corners of the mouth
• hair shedding
• restless legs syndrome, especially at night
• difficulty swallowing from thin webs in the esophagus (rare)

In children, iron deficiency can affect growth, behavior, attention and learning. Older adults may notice worsening angina or heart failure.

Causes

Iron deficiency happens when the body loses more iron than it absorbs, needs more than it gets, or cannot absorb what it eats.

Blood loss (the most common cause in adults)

• Heavy periods: the leading cause in women of reproductive age. See menorrhagia. Fibroids and bleeding disorders are common underlying reasons.
• Bleeding in the gut: often slow and invisible. Causes include peptic ulcers, gastritis from NSAIDs or aspirin, colorectal cancer and polyps, angiodysplasia (fragile blood vessels) and inflammatory bowel disease.
• Frequent blood donation, and less commonly urinary tract bleeding or nosebleeds.

Increased need

• Pregnancy: iron needs roughly double, especially in the second and third trimesters.
• Rapid growth: in infants, toddlers and teenagers.
• Endurance training: runners lose some iron through sweat, the gut and red cell breakdown in the feet.

Low intake

• vegetarian or vegan diets that do not include enough iron-rich plant foods
• toddlers who drink a lot of cow's milk (more than 16 to 24 oz, or 500 to 700 ml, a day), which is low in iron and fills them up
• restrictive or poor diets in older adults

Poor absorption

• celiac disease
• H. pylori stomach infection and atrophic gastritis
• weight-loss (bariatric) surgery or other stomach and bowel surgery
• long-term stomach acid-reducing medicines
• Crohn's disease

Worldwide, hookworm and other parasites are also major causes.

Iron deficiency anemia in women and in pregnancy

Women of reproductive age lose iron each month through periods, and they need about 18 mg of iron a day compared with 8 mg for adult men. Pregnancy raises the need to 27 mg a day. Iron deficiency in pregnancy is linked with preterm birth, low birth weight and greater tiredness after delivery, which is why hemoglobin is checked early in pregnancy and again later. Women with heavy periods should have their iron checked, and the cause of the heavy bleeding treated, not just the anemia.

How it is diagnosed

Ferritin rises during infection and inflammation, so it can look normal despite iron deficiency in people with chronic illness. Doctors then use transferrin saturation and other markers. Thalassemia trait also causes small red cells but with normal iron levels, and anemia of chronic disease can look similar.

Finding the cause

The anemia is a sign, not a diagnosis. Your doctor will ask about periods, diet, bowel habits, blood in the stool, indigestion, NSAID use, weight loss and family history of bowel cancer. Tests may include:

• celiac antibody blood test
• urine test for blood
• stool tests or H. pylori testing
• upper endoscopy and colonoscopy: recommended by the American Gastroenterological Association for men and for women past menopause with iron deficiency anemia, and for younger people with gut symptoms or no other explanation

Treatment

Iron tablets

Oral iron, such as ferrous sulfate, is the usual first treatment. Your doctor will advise the dose.

• Taking iron once a day or every other day is often as effective as more frequent doses, with fewer side effects.
• Take it on an empty stomach if you can, or with a little food if it upsets your stomach.
• Take it with vitamin C or orange juice to boost absorption.
• Avoid tea, coffee, milk, calcium supplements and antacids for about 2 hours either side of the dose.
• Side effects include constipation, nausea, stomach cramps and black stools. Black stools from iron are expected and harmless, but tarry, sticky black stools with dizziness need checking.

Hemoglobin usually rises within 2 to 4 weeks and normalizes by 6 to 8 weeks. Keep taking iron for about 3 months after that to refill stores, until ferritin is normal.

Intravenous iron

An iron infusion replenishes stores in one or two visits. It is used when tablets are not tolerated or not working, when absorption is poor (celiac disease, IBD, bariatric surgery), with ongoing blood loss, in later pregnancy, in chronic kidney disease, or when quick correction is needed before surgery.

Blood transfusion

Reserved for very severe anemia, heart symptoms or active heavy bleeding.

Treating the cause

This might mean treating heavy periods with hormonal options or a procedure, stopping NSAIDs, treating ulcers or H. pylori, a gluten-free diet for celiac disease, or removing polyps or cancers.

Iron-rich foods

• Heme iron (best absorbed): red meat, liver, poultry, fish and shellfish.
• Non-heme iron: beans, lentils, chickpeas, tofu, fortified breakfast cereals, dark leafy greens, nuts, seeds and dried fruit.

Pair plant iron with vitamin C (peppers, citrus, tomatoes, strawberries) to improve absorption. Diet alone rarely corrects established anemia, but it helps prevent recurrence. Do not take iron supplements without a confirmed deficiency, because excess iron can be harmful, and keep all iron products out of children's reach: iron overdose is dangerous for young children.

Frequently asked questions

What are the first signs of iron deficiency anemia?

Early signs are often tiredness, low energy, reduced exercise tolerance, headaches and feeling cold. Pale skin, breathlessness on stairs, a fast heartbeat, brittle nails and cravings for ice may follow. Because symptoms creep up slowly, many people do not notice them until a blood test shows anemia.

What ferritin level indicates iron deficiency?

A ferritin below about 30 ng/mL strongly suggests iron deficiency, and below 15 ng/mL confirms it. Ferritin can be falsely normal or high during infection, inflammation or liver disease, so doctors may also use transferrin saturation and other tests in those situations.

How long does it take to recover from iron deficiency anemia?

Many people feel more energetic within 1 to 2 weeks of starting iron. Hemoglobin usually rises within 2 to 4 weeks and returns to normal in about 6 to 8 weeks. Iron is continued for around 3 more months to refill stores. IV iron works faster.

Why do I need a colonoscopy for iron deficiency anemia?

In men and in women past menopause, iron deficiency is often caused by slow bleeding in the gut that you cannot see, including ulcers, polyps and bowel cancer. Endoscopy and colonoscopy find these causes. Younger women may also need them if periods do not explain the deficiency or there are gut symptoms.

Can iron deficiency anemia be serious?

Usually it is mild and easily treated, but severe anemia can strain the heart, causing chest pain, palpitations and heart failure, especially in older adults. It can also be the first sign of a serious problem such as bowel cancer. In pregnancy it raises the risk of preterm birth and low birth weight.

Why does iron deficiency cause ice cravings?

Craving and chewing ice, called pagophagia, is a well-recognized sign of iron deficiency. The reason is not fully understood. Cravings usually disappear quickly once iron treatment starts, often before hemoglobin has fully recovered.