Beyond tired: What anemia is and how it affects the body

Published February 13, 2026

Anemia is a condition where the blood doesn’t have enough healthy red blood cells or hemoglobin. Hemoglobin is an iron-rich protein inside red blood cells that carries oxygen. When levels are low, or red blood cells don’t function properly, the blood can’t deliver as much oxygen from the lungs to the rest of the body. This can lead to symptoms like¹,²

• Ongoing fatigue or weakness
• Difficulty concentrating or thinking clearly
• Shortness of breath
• Dizziness
• Headaches
• Cold hands or feet
• Pale or yellow skin
• Brittle nails
• Hair shedding
• Irritability
•  A fast or irregular heartbeat
• A pounding or “whooshing” sound in the ears

Early signs and symptoms of anemia are often overlooked. Many people don’t realize they have anemia until it shows up on a blood test. Without treatment, symptoms can worsen over time and begin to affect overall quality of life.¹

Is anemia the same as iron deficiency anemia?

Not exactly. Anemia is a general term that means the blood has lower-than-normal amounts of red blood cells or hemoglobin. Iron deficiency anemia is one specific type of anemia that develops when the body doesn’t have enough iron. So while all iron deficiency anemia is anemia, not all anemia is caused by iron deficiency.¹

Why does anemia happen?

Anemia can happen for different reasons. Sometimes the body doesn’t make enough healthy red blood cells. Other times, they’re destroyed too quickly or lost through bleeding.¹⁻³

Red blood cell production is disrupted

Your body needs the right amount of nutrients and hormones to make healthy red blood cells and hemoglobin. Some health conditions can also interfere with nutrient absorption or affect the body’s ability to make red blood cells. This can be caused by

• Low iron, vitamin B12, or folate (folic acid)
• Kidney, liver, or thyroid disease
• Autoimmune conditions (celiac disease, pernicious anemia)
• Inherited conditions (bone marrow failure syndromes, iron-refractory iron deficiency anemia)
• Chronic inflammation
• Certain cancers or cancer treatments

Red blood cells are destroyed too quickly

Sometimes red blood cells are broken down or destroyed before the end of their natural lifespan, faster than the body can replace them. This can be caused by

• Autoimmune conditions (autoimmune hemolytic anemia)
• Inherited conditions (sickle cell disease, thalassemia, hereditary spherocytosis)
• Certain infections, medications, or toxins

Red blood cells are lost through bleeding

Blood loss reduces the number of red blood cells in circulation and can also lead to low iron levels. This can be caused by

• Heavy or long menstrual periods
• Frequent, heavy nosebleeds
• Gastrointestinal bleeding (ulcers, colon polyps)
• Injury, surgery, or childbirth
• Inherited bleeding disorders (von Willebrand disease)

Anemia can also develop when the body needs more iron than usual, such as during pregnancy or periods of rapid growth. It can also stem from factors like low stomach acid, chronic infections, or the use of certain medications.

How can blood tests help identify anemia?¹⁻⁴

Red blood cells have a natural lifespan of about 120 days. From the moment they’re made to the time they’re recycled, a lot has to go right. Anemia can develop when something disrupts that journey, and blood tests help point to where the issue may be.

The journey begins in the bone marrow, where over about a week, stem cells mature into early red blood cells called reticulocytes. This process depends on iron, vitamin B12, folate, and a kidney hormone called erythropoietin (EPO). Inflammation can further disrupt this process by preventing the body from accessing its own iron stores. Even when this process is affected, production often continues, but the cells may differ in size or shape, carry less hemoglobin, or have shorter lifespans.

Reticulocytes are then released into the bloodstream, where they become fully mature red blood cells within a day or two. During this stage, they take on a flexible, disc-like shape that allows them to bend and move through blood vessels as efficient oxygen carriers.

For most of their lifespan, red blood cells circulate through the bloodstream, traveling to the lungs to pick up oxygen and delivering it to tissues throughout the body. But over time, the constant work of squeezing through narrow vessels causes wear and tear. As this happens, they lose flexibility and efficiency and the body marks them for removal.

At the end of their lifespan, or sooner if they’re damaged or differ in shape, red blood cells marked for removal are cleared by the spleen and liver. Iron is recycled for future use, and hemoglobin is broken down into bilirubin to be processed by the liver and removed from the body.

Blood tests to help identify anemia

What is measured and what it can show¹⁻⁴

No doctor visit is required to buy your own lab test at questhealth.com. PWNHealth and its affiliates review your purchase to ensure it is medically appropriate before submitting the test order for processing. PWNHealth also reviews your test results and will contact you directly if they require prompt attention. Included in each purchase is the ability to discuss your test results with an independent healthcare provider; however, you are also encouraged to speak with your primary healthcare provider.