Tired Blood: A Primer on Anemia

Anemia is a blood disorder that affects more than 30 percent of the world’s population.1,2 Anemia occurs when there are not enough red blood cells (RBCs) in the body or their ability to carry oxygen throughout the body is lowered.1–5 .

Signs, Symptoms, and Complications of Anemia

Anemia actually isn’t a disease. Rather, it’s a condition that occurs due to other health problems, such as poor nutrition, thyroid disease, autoimmune disorders, or even an injury.2,4 Its signs and symptoms exist on a spectrum, depending on how low the RBC count is, RBC functioning, and how quickly the condition develops.7 Mild anemia often has no noticeable signs or symptoms; when symptoms do occur, they typically include the following:1–4,6

  • Consistent fatigue
  • General weakness
  • Pale or yellowish skin
  • Shortness of breath
  • Dizziness
  • Pounding or “whooshing” in your ears
  • Cold hands or feet
  • Fast or irregular pulse

Causes of Anemia

The exact causes of anemia aren’t always clear, but experts know that the condition can be acquired  or inherited.6 Anemia generally falls into three categories: 1) the body is making too few RBCs, 2) the body is destroying too many RBCs, and/or 3) the body is losing RBCs more quickly than it can produce them.

Too few RBCs. To make enough healthy RBCs and hemoglobin, the body needs iron, vitamin B12, folate.1–3,5 Poor diet, some cancers, autoimmune disorders, and pregnancy can all affect the levels of these nutrients. Potential inherited causes include Diamond-Blackfan anemia and Fanconi anemia.6

Destruction of RBCs. RBCs have a lifespan of about 120 days, but they can be destroyed by the body before they reach their natural expiration. Sometimes, RBCs are wiped out in such great numbers that production in the bone marrow cannot keep up.6 Some acquired causes of anemia are functional, such as physical damage to RBCs or an infection (e.g., lupus or hepatitis) that impacts their production. Inherited causes of RBC destruction include sickle cell anemia and thalassemia.8

Loss of RBCs. Major blood loss can lead to low levels of iron in the body, in addition to rapidly losing RBCs. Without iron, the body is unable to make enough RBCs, and the RBCs it does make will have less hemoglobin than normal.6 In addition to acute trauma (e.g., due to an accident or surgery), major blood loss can stem from chronic conditions, such as heavy menstrual bleeding or bleeding peptic ulcers. 

Diagnosis and Treatment of Anemia

If you suspect you have anemia, ask your doctor about being tested during your next checkup. The symptoms of anemia may seem general, but it can be easily diagnosed during routine or targeted blood tests. If your doctor suspects you have gastrointestinal bleeding, they likely will order a fecal occult blood test, upper endoscopy, and/or colonoscopy to help with diagnosis and guide treatment.9 

The type of treatment one receives for anemia depends on the type of anemia one has. Generally speaking, adding iron-rich foods to your diet, such as certain meats and green, leafy vegetables, is a simple way to prevent and treat the condition. Your doctor may also consider providing you with iron supplements.2 

If anemia is due to a chronic disease, such as kidney failure, treatment of the underlying illness will often increase RBC count. Aplastic anemia, which occurs when bone marrow stops producing red blood cells, may be treated more directly with prescribed medications and blood transfusions.2,15

Risk Factors of Anemia

There are several risk factors for anemia.

  • Age. Infants between 6 and 12 months of age, children 1 to 2 years of age, teenagers, and older adults, especially those over the age of 65 years, are at higher risk of developing anemia.10,11


  • Family history and genetics. Von Willebrand disease is an inherited bleeding disorder that affects the blood’s ability to clot, resulting  in chronic blood loss.12 This can increase the risk of iron-deficiency anemia from trauma, surgery, or heavy menstrual periods.12,13 For similar reasons, hemophilia is another risk factor.14


  • Lifestyle habits. Certain activities such regularly donating blood and participating in contact sports can increase the risk of developing anemia due to blood loss.9 Endurance athletes, especially young female athletes, are more susceptible to anemia. Endurance athletes lose iron through their gastrointestinal tracts and breakdown of RBCs, called hemolysis, can be caused by strong muscle contractions.8 For example, the impact of feet repeatedly striking the ground, such as with marathon runners, can increase the risk of developing anemia. 


  • Diet. Food choices can be one of the most important risk factors for developing anemia. Not eating enough iron-rich foods, such as certain meats or fish or leafy, green vegetables, may result in an iron deficiency, which can cause anemia.8,10 Following a pescatarian, vegetarian, and vegan diet can increase the risk of developing anemia.


  • Female sex. Women between the ages of 14 and 50 years need more iron than boys and men of the same age. Women are at higher risk for iron-deficiency anemia under some circumstances due to blood loss. This includes menstruation and during pregnancy, after delivery, and when breastfeeding.8

Bottom Line

Anemia is one of the world’s most common blood disorders, affecting about 30 percent of the world’s population and more than three million Americans.1,2 There are many different types of anemia, but all are marked by a deficiency in RBCs throughout the body. Some of the most common symptoms of anemia include general fatigue and weakness, sallow skin, and cold extremities. Anemia can be easily diagnosed during routine blood tests, which can help guide diagnosis and treatment. Treatment can range from simple dietary modifications to blood transfusions, depending on the nature of the anemia.

While most people with anemia can live healthy lives, the long-term outlook for the condition depends on the cause and treatment response. If left untreated, anemia can lead to a number of health complications, such as heart failure, severe weakness, and compromised immunity. Fortunately, most types of anemia are very treatable.


1. Anaemia. World Health Organization website. https://www.who.int/health-topics/anaemia#tab=tab_1. Accessed 18 Oct 2021.

2. Anemia. American Society of Hematology. https://www.hematology.org/education/patients/anemia. Accessed 18 Oct 2021.

3. Duyff RL. Academy of Nutrition and Dietetics Complete Food and Nutrition Guide. New York, NY: Academy of Nutrition and Dietetics; 2017:722-726.

4. NIH. Anemia. National Heart, Lung, and Blood Institute website. https://www.nhlbi.nih.gov/health-topics/anemia. Accessed 18 Oct 2021. 

5. CDC. Infant and Toddler Nutrition: Definitions. Updated 30 Oct 2020. The Center for Disease Control and Prevention. https://www.cdc.gov/nutrition/infantandtoddlernutrition/definitions.html#Anemia. Accessed 25 Oct 2021. 

6. USHHS. Sept 2011. Your Guide to Anemia. National Heart, Lung, and Blood Institute website. https://www.nhlbi.nih.gov/files/docs/public/blood/anemia-yg.pdf. Accessed 18 Oct 2021.

7. How can one donation help multiple people? The American Red Cross website. https://www.redcrossblood.org/donate-blood/how-to-donate/types-of-blood-donations/blood-components.html. Accessed 1 Nov 2021.

8. Hemolytic Anemia. Johns Hopkins Medicine website. https://www.hopkinsmedicine.org/health/conditions-and-diseases/hemolytic-anemia. Accessed 1 Nov 2021.

9. NIH. Iron-Deficiency Anemia. National Heart, Lung, and Blood Institute website. https://www.nhlbi.nih.gov/health-topics/iron-deficiency-anemia. Accessed 18 Oct 2021.

10. Lopez A, Cacoub P, Macdougall IC, Peyrin-Biroulet L. Iron deficiency anaemia. The Lancet. 2016;387(10021):907-916.

11. Gupta PM, Perrine CH, Mei Z, Scanlon KS. Iron, anemia, and Iion deficiency anemia among young children in the United States. Nutrients. 2016;8(6):330.

12. CDC. Updated 1 Apr 2021. What is von Willebrand Disease? Center for Disease Control and Prevention website. https://www.cdc.gov/ncbddd/vwd/facts.html. Accessed 2 Nov 2021.

13. Iron. Updated 24 Aug 2021. Center for Disease Control and Prevention website. https://www.cdc.gov/nutrition/infantandtoddlernutrition/vitamins-minerals/iron.html. Accessed 18 Oct 2021.

14. NIH. Updated 11 Sep 2019. Bleeding Disorders. National Heart, Lung, and Blood Institute website. https://www.nhlbi.nih.gov/health-topics/bleeding-disorders. Accessed 2 Nov 2021.

15. Aplastic Anemia. The Sidney Kimmel Comprehensive Cancer Center website. https://www.hopkinsmedicine.org/kimmel_cancer_center/cancers_we_treat/blood_bone_marrow_cancers/aplastic_anemia.html. Accessed 2 Nov 2021.    

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