What Causes Anemia?

Medically reviewed by Deborah Weatherspoon, PhD, RN, CRNA on January 3, 2018 Written by Verneda Lights and Brian Wu

Anemia happens when the number of healthy red blood cells in your body is too low. Red blood cells carry oxygen to all of the body’s tissues, so a low red blood cell count indicates that the amount of oxygen in your blood is lower than it should... Read More

What is anemia?

Anemia happens when the number of healthy red blood cells in your body is too low. Red blood cells carry oxygen to all of the body’s tissues, so a low red blood cell count indicates that the amount of oxygen in your blood is lower than it should be. Many of the symptoms of anemia are caused by decreased oxygen delivery to the body’s vital tissues and organs.

Anemia is measured according to the amount of hemoglobin, which is the protein within red blood cells that carries oxygen from the lungs to the body’s tissues. According to the Cleveland Clinic, about 3.4 million Americans suffer from anemia. Women and people with chronic diseases such as cancer have the highest risk of developing anemia.

What causes anemia?

Dietary iron, vitamin B-12, and folate are essential for red blood cells to mature in the body. Normally, 0.8 to 1 percent of the body’s red blood cells are replaced every day, and the average lifespan for red cells is 100 to 120 days. In general, any process that has a negative effect on this balance between red blood cell production and destruction can cause anemia.

Causes of anemia are generally divided into those that decrease red blood cell production and those that increase red blood cell destruction.

Factors that decrease red blood cell production include:

On the other hand, any disorder that destroys red blood cells at a rate that’s faster than they’re made can cause anemia. Factors that increase red blood cell destruction include:

Overall, however, iron deficiency is the most common cause of anemia. Iron intake is a major index for the health assessment of nations. According to the World Health Organization (WHO), an estimated 2 billion people worldwide have anemia, and many have it because of iron deficiency.

Daily nutritional requirements and anemia

Daily requirements for vitamins and iron vary according to sex and age. Women need more iron and folate than men because of iron losses during their menstrual cycle and fetal development during pregnancy and lactation.


According to the Office of Dietary Supplements (ODS), the recommended daily iron intake for women age 19 to 50 is 18 milligrams (mg). The daily iron intake for men of the same age range is 8 mg. During pregnancy, daily iron intake should increase to 27 mg, but women who are breastfeeding only need 9 mg per day.

Men and women over the age of 50 require 8 mg of iron daily. A supplement may be needed if adequate iron levels can’t be reached through diet alone.

Good sources of dietary iron include:

  • chicken and beef liver
  • dark turkey meat
  • red meats, such as beef
  • seafood
  • fortified cereals
  • oatmeal
  • lentils
  • beans
  • spinach


Folate is the form of folic acid that occurs naturally in the body. Males and females over the age of 14 require 400 micrograms of dietary folate equivalents (mcg/DFE) per day. For women who are pregnant or breastfeeding, the recommended intake increases to 600 mcg/DFE (pregnant) and 500 mcg/DFE (lactating) per day.

Examples of foods rich in folate are:

  • beef liver
  • lentils
  • spinach
  • great northern beans
  • asparagus

You can also add folic acid to your diet with fortified cereals and breads.

Vitamin B-12

The daily adult recommendation for vitamin B-12 is 2.4 mcg. Women and teens who are pregnant need 2.6 mcg per day, and women who are breastfeeding require 2.8 mcg daily.

Beef liver and clams are two of the best sources of vitamin B-12. Other good sources include:

  • fish
  • meat
  • poultry
  • eggs
  • other dairy products

Vitamin B-12 is also available as a supplement for those who don’t get enough from their diet alone.

Shop for vitamin B-12 supplements.

What are the symptoms of anemia?

People with anemia appear pale and may often complain of being cold. They may also have lightheadedness or dizziness, especially when they are active or standing up. Some people with anemia have unusual cravings such as wanting to eat ice, clay, or dirt. They often complain of feeling tired and have problems with constipation and concentration. Some anemias can cause inflammation of the tongue, resulting in a smooth, glossy, red, and often painful tongue.

If anemia is severe, fainting may occur. Other symptoms include brittle nails, shortness of breath, and chest pains. Blood oxygen levels can be so low that a person with severe anemia can have a heart attack.

A physical exam that your doctor does may show:

People with symptoms of anemia should seek medical attention.

How is anemia diagnosed?

A diagnosis of anemia begins with your health history, and that of your family, and a physical exam. Laboratory tests help doctors to find out the cause of the anemia. A family history of certain types of anemia such as sickle cell anemia can be helpful. A history of exposure to toxic agents in the home or workplace might point to an environmental cause.

Tests to diagnose anemia include:

Complete blood count (CBC)

This blood test tells doctors the number and size of the RBCs. It also shows if other blood cells like white blood cells and platelets are normal.

Serum iron levels

This blood test shows if iron deficiency is the cause of anemia.

Ferritin test

This blood test analyzes iron stores.

Vitamin B-12 test

This blood test shows vitamin B-12 levels and determines if they are too low.

Folate test

This blood test reveals if serum folate levels are too low.

Stool test for occult blood

This test applies a chemical to a stool specimen to see if blood is present. If the test is positive, it means that blood is being lost anywhere in the gastrointestinal tract, from the mouth to the rectum. Problems like stomach ulcers, ulcerative colitis, and colon cancer can cause blood to be in stool.

Additional tests

Based on the results of these tests, doctors may order additional studies such as an upper GI, a barium enema, chest X-rays, or a CT scan of your abdomen.

How to treat anemia

The treatment for anemia depends on its cause. Anemia caused by inadequate amounts of dietary iron, vitamin B-12, and folate is treated with nutritional supplements. In some cases, injections of B-12 are needed as it isn’t absorbed properly from the digestive tract. Your doctor and nutritionist can prescribe a diet that contains proper amounts of vitamins, minerals, and other nutrients. A proper diet can help prevent this kind of anemia from recurring.

In some cases, if the anemia is severe, doctors use erythropoietin injections to increase red blood cell production in the bone marrow. If bleeding occurs or the hemoglobin level is very low, a blood transfusion may be necessary.

What is the outlook for anemia?

The long-term outlook for anemia depends on the cause and the response to treatment. Anemia is very treatable, but it can be dangerous if it’s left untreated. Pay attention to food labels and invest in a multivitamin to ensure that you’re getting the recommended daily amount of iron.

Talk to your doctor if you’re experiencing any of the symptoms of anemia, especially if you have a family history of anemia. Your doctor will most likely get you started on a diet or supplement regimen to increase your iron intake.

An iron deficiency may also be a sign of more serious medical conditions, so it’s important to pay attention to your body. In most cases, just tweaking your diet or taking an iron supplement can solve your anemia.

Shop for iron supplements.

Medically reviewed by Deborah Weatherspoon, PhD, RN, CRNA on January 3, 2018 Written by Verneda Lights and Brian Wu

44 possible conditions

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This feature is for informational purposes only and should not be used to diagnose. Please consult a healthcare professional if you have health concerns.

Medically reviewed by Deborah Weatherspoon, PhD, RN, CRNA on January 3, 2018 Written by Verneda Lights and Brian Wu