What causes anemia? 45 possible conditions

What Is Anemia?

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

Anemia is measured according to the amount of hemoglobin, the protein that carries oxygen, in RBCs. The World Health Organization (WHO) defines anemia as less than 13 grams of hemoglobin per deciliter for men, and less than 12 grams of hemoglobin per deciliter for women. Approximately three million Americans suffer from anemia. Women and people with chronic diseases are at highest risk of anemia.

What Causes Anemia?

Dietary iron, B12, and folate are essential for RBCs to mature in the body. Normally, red cells are replaced at a daily rate of .8 to one percent 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 RBC production and destruction can cause anemia. Causes of anemia are generally divided into two categories: those that decrease RBC production and those that increase RBC destruction.

Some factors that decrease red cell production are:

  • inadequate stimulation of red cell production by the hormone erythropoietin (secreted by the kidneys)
  • inadequate dietary intake of iron, B12, and folate
  • hypothyroidism

Iron Deficiency Is the Most Common Cause of Anemia

Iron intake is a major index for the health assessment of nations. According to the WHO, an estimated 2.15 billion individuals worldwide have iron deficiency anemia.

Daily Nutritional Requirements and Anemia

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


The National Institutes of Health (NIH) states that the daily iron intake for women aged 18 to 50 is 18 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 breast-feeding need only nine mg per day. Men and women over the age of 50 require nine mg of iron daily, according to the Office of Dietary Supplements. A supplement may be needed if adequate iron levels cannot be reached through diet alone. Good sources of dietary iron include chicken and beef liver, oysters, dark turkey meat, beef, fortified cereals, oatmeal, lentils, beans, and spinach.

Folate/Folic Acid

Folate is the form of folic acid that occurs naturally in the body. Males and females over the age of 14 require 400 ?g of folic acid a day. For women who are pregnant or breast-feeding, the demand for folic acid increases to 500 ?g/day. Examples of foods rich in folic acid are fortified cereals, beef liver, lentils, spinach, great northern beans, and asparagus.


Daily adult requirement for vitamin B12 is 2.4 mcg. Pregnant women and teens need 2.6 mcg per day, and women who are breast-feeding require 2.8 mcg daily (Office of Dietary Supplements, NIH, 2011). Beef liver and clams are two of the best sources of B12. Other good sources include fish, meat, poultry, eggs, and other dairy products. B12 is also available as a vitamin supplement for those who don’t get enough from diet alone.

Factors That Increase RBC Destruction

Any disorder that destroys RBCs at a rate that is faster than they are made can cause anemia. Examples of disorders that cause anemia due to increased destruction of red cells are:

  • hemorrhage from accidents, gastrointestinal lesions, menstruation, childbirth, excessive uterine bleeding, or surgery
  • cirrhosis (scarring of the liver)
  • fibrosis (scar tissue) within the bone marrow
  • hemolysis (rupture) of red cells (can occur with some medications or Rh incompatibility)
  • disorders of the liver and spleen
  • genetic disorders such as G-6-PD deficiency, thalassemia, and sickle cell anemia

What Are the Symptoms of Anemia?

People with anemia appear pale and may often complain of being cold. They may also have light-headedness, especially when they are active or standing up. 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 can have a heart attack. 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.

Physical exam may show:

  • high or low blood pressure
  • pale skin
  • jaundice
  • increased heart rate
  • heart murmur
  • enlarged lymph nodes
  • enlarged spleen or liver

People with symptoms of anemia should seek medical attention.

How Is Anemia Diagnosed?

A diagnosis of anemia begins with the family and health history of a patient and a physical examination. Laboratory tests help doctors to find out the cause of the anemia. A family history of certain types of anemia such as sickle cell, can be helpful. Also, a history of exposure to toxic agents in the home or work place 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 WBCs and platelets are normal.

Serum Iron Levels

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

Ferritin Test

This blood test analyzes iron stores.

B12 Test

This blood test shows B12 levels and determines if they are too low.

Folic Acid Test

This blood test reveals if folic acid 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.

Based on the results of these tests, doctors may order additional studies such as an upper GI, barium enema, Chest x-rays, or CAT scan of the abdomen.

Treatment of Anemia

The treatment of anemia depends upon its cause. Anemia caused by inadequate amounts of dietary iron, B12, and folic acid is treated with nutritional supplements. The doctor and nutritionist can prescribe a diet that contains proper amounts of vitamins, minerals, and other nutrients. Proper diet can help to prevent recurrence of this kind of anemia. In some cases, if anemia is severe, doctors use erythropoietin injections to increase RBC production in the bone marrow. If bleeding occurs or the hemoglobin level is very low, a blood transfusion may be necessary. The prognosis for anemia depends on the cause and the response to treatment.

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See a list of possible causes in order from the most common to the least.


Iron Deficiency Anemia

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Folic Acid Deficiency Anemia

Folic acid deficiency anemia is caused by having too little vitamin B9 (folate) in your blood. Folate is necessary for your body to make new red blood cells. Red blood cells are needed to carry oxygen to your organs. I...

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Thalassemia is an inherited blood disorder that results in excessive destruction of red blood cells (anemia). Symptoms depend on its severity, and can range from minor anemia to enlargement of organs or fetal death.

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Ulcerative Colitis

In UC, the lining of the large intestine and the rectum become inflamed. This produces tiny sores or ulcers on the lining of the colon, often accompanied by diarrhea and cramping.

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Hookworm Infections

Hookworms are parasites that affect the small intestine and lungs. The first sign of infection is usually a rash where the parasite entered the skin, followed by diarrhea.

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Megaloblastic Anemia

Megaloblastic anemia is a blood disorder marked by the appearance of very large red blood cells that crowd out healthy cells, causing anemia. Numbness or tingling in hands and feet is common sign.

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Amebiasis is a parasitic infection, common in tropical countries and caused by contaminated water. Symptoms can be severe and usually start one to four weeks after exposure.

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Bleeding Esophageal Varices

This condition is considered a medical emergency. Urgent care may be required.

Bleeding esophageal varices occur when swollen veins in your lower esophagus rupture and bleed due to excess pressure. This condition is a medical emergency and must be dealt with promptly.

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Hypovolemic Shock

This condition is considered a medical emergency. Urgent care may be required.

Hypovolemic shock is a life-threatening condition that results when you lose more than 20 percent (one-fifth) of your body's blood or fluid supply. This severe fluid loss makes it impossible for the heart to pum...

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Celiac Disease (Gluten Intolerance)

Celiac disease is a digestive disorder caused by an immune reaction to gluten. Symptoms vary but can include arthritis, fatigue, and abdominal symptoms.

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Failure to Thrive

Your child may be diagnosed with failure to thrive if he or she falls below a healthy weight and shows signs of emotional underdevelopment. Typically, failure to thrive is discovered during a child's infant years. Idea...

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Pernicious Anemia

Pernicious anemia (PA) is an autoimmune disorder in which the body fails to make enough healthy red blood cells (RBCs), resulting in vitamin B-12 deficiency. Most people experience a burning or sore tongue.

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The thyroid gland produces a hormone that controls how your cells use energy (metabolize). Hypothyroidism occurs when the body doesn't produce enough. Untreated, it can cause comlications like obesity and heart disease.

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Malaria is a life-threatening disease. It is typically transmitted through the bite of a mosquito infected with Anopheles. Nausea, chills, fever, and diarrhea are common symptoms.

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Leukemia is a cancer of the blood cells. Excessive sweating at night, constant fatigue, weight loss, bone pain, and easy bleeding or bruising are all signs of this disease.

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Hemophilia A

Hemophilia A (factor VIII deficiency) is the most common form of the blood clotting disorder hemophilia. It can cause prolonged bleeding, tight joints, and unexplained bruising.

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Acquired Platelet Function Disorder

Platelets are a type of blood cell. They play an important role in healing from injuries. Platelets help your body to form blood clots and stop bleeding. Some people’s platelets don’t function the way the...

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Drug-Induced Immune Hemolytic Anemia

Drug-induced immune hemolytic anemia (DIIHA) is a rare blood disorder in which your immune system begins attacking your red blood cells. Symptoms include dark urine, fast heartbeat, and jaundice.

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Sickle Cell Anemia

Sickle cell anemia is a genetic disease that causes red blood cells to have an abnormal shape, causing blood flow problems. This can lead to tissue damage and pain, as well as enlarged spleen, anemia, and other symptoms.

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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.
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