Anemia means your blood does not carry enough oxygen to your body's tissues

Anemia happens when you do not have enough healthy red blood cells, or when the red blood cells you have cannot carry oxygen properly. Red blood cells contain a protein called hemoglobin, which picks up oxygen in your lungs and delivers it everywhere else in your body. When hemoglobin levels drop too low, your organs and muscles do not get the oxygen they need to work well.

This is not the same as low blood pressure or heart disease, though anemia can make those conditions worse. It is also not contagious. Anemia is a sign that something else is going on in your body — either your bone marrow is not making enough red blood cells, your red blood cells are being destroyed faster than they should be, or you are losing blood somewhere.

Key Takeaways

  • Anemia occurs when your blood does not have enough healthy red blood cells to carry oxygen to your body's tissues.
  • Common symptoms include fatigue, shortness of breath, dizziness, pale skin, and cold hands or feet.
  • A simple blood test called a complete blood count (CBC) is how doctors diagnose anemia.
  • The cause matters: anemia can result from iron deficiency, vitamin deficiency, chronic disease, bleeding, or bone marrow problems.
  • Treatment depends on the type and cause, and ranges from dietary changes to medication to transfusions in severe cases.

Why your body needs red blood cells

Every cell in your body needs oxygen to produce energy. Your lungs breathe in oxygen, and red blood cells pick it up and transport it through your bloodstream. When you do not have enough red blood cells, or when the ones you have are not working properly, oxygen delivery slows down. Your heart has to work harder to pump blood faster, trying to make up for the shortage.

This is why anemia makes you tired — your muscles are not getting the oxygen they need. It is also why you might feel short of breath during normal activities. Your body is essentially running on a lower fuel supply than it should be.

Symptoms that suggest anemia

The symptoms of anemia develop gradually and depend on how severe it is. Mild anemia might cause no noticeable symptoms at all. Moderate to severe anemia often causes fatigue that does not improve with rest, shortness of breath during light activity, dizziness or lightheadedness, headaches, pale or yellowish skin, cold hands and feet, or chest pain or irregular heartbeat.

Some people notice they cannot concentrate as well as usual, or that they feel irritable. These happen because your brain is not getting as much oxygen as it normally does. If you have symptoms that last more than a few weeks, or if they are getting worse, that is when to see a doctor.

How doctors test for anemia

A doctor diagnoses anemia with a blood test called a complete blood count, or CBC. This test measures how many red blood cells you have and how much hemoglobin they contain. The test also measures hematocrit, which is the percentage of your blood that is made up of red blood cells. If your hemoglobin or hematocrit is below the normal range for your age and sex, you have anemia.

The normal ranges vary slightly between men and women, and they change as you age. A doctor will compare your results to the standard ranges and tell you whether your levels are low. If the CBC shows anemia, your doctor will usually order additional tests to find out why — these might include tests for iron levels, vitamin B12, folate, or thyroid function, depending on what your doctor suspects is causing the problem.

The main types of anemia and what causes them

Iron deficiency anemia is the most common type worldwide. It happens when your body does not have enough iron to make hemoglobin. This can occur from heavy menstrual bleeding, bleeding in the digestive tract, not eating enough iron-rich foods, or poor absorption of iron in your gut.

Vitamin deficiency anemia results from low levels of vitamin B12 or folate, both of which your body needs to make red blood cells. B12 deficiency can happen if you have digestive problems, follow a strict vegetarian diet, or have had stomach surgery. Folate deficiency usually comes from not eating enough leafy greens, legumes, or fortified grains.

Anemia of chronic disease occurs when you have a long-term illness like kidney disease, cancer, rheumatoid arthritis, or heart disease. These conditions interfere with your body's ability to make red blood cells or use iron properly.

Hemolytic anemia happens when red blood cells are destroyed faster than your bone marrow can replace them. This can be caused by autoimmune disease, infections, certain medications, or inherited conditions like sickle cell disease.

Aplastic anemia is rare and serious. Your bone marrow stops making enough red blood cells, white blood cells, and platelets. This can be caused by certain medications, radiation, chemotherapy, infections, or autoimmune disease.

What happens after diagnosis

Once your doctor knows you have anemia, the next step is finding the cause. This matters because treatment depends on what is causing the problem. If you have iron deficiency anemia from heavy periods, you need iron supplementation and possibly treatment for the bleeding. If you have B12 deficiency from poor absorption, you might need B12 injections rather than pills. If you have anemia from chronic kidney disease, you might need medication to stimulate red blood cell production.

Your doctor will discuss the results with you and explain what is happening. They will also talk about treatment options and what to expect. Some types of anemia improve quickly with the right treatment; others require ongoing management. In severe cases where anemia is causing serious symptoms or complications, you might need a blood transfusion while treatment takes effect.

When to see a doctor about anemia symptoms

You should contact a doctor if you have persistent fatigue that does not improve with sleep, shortness of breath during normal activities, dizziness that affects your daily life, or pale skin that is new for you. You should also see a doctor if you have a known condition like kidney disease or cancer and develop new symptoms of anemia, or if you are taking medications that can cause anemia and notice changes in how you feel.

If you have severe chest pain, severe shortness of breath, fainting, or confusion, go to an emergency room or call emergency services. These can be signs of severe anemia or another serious condition that needs immediate care.

Frequently Asked Questions

Can anemia go away on its own?

Some types can improve without treatment if the cause resolves — for example, if you stop taking a medication that was causing anemia. Most types require treatment to improve. Iron deficiency anemia needs iron supplementation, B12 deficiency needs B12 replacement, and chronic disease anemia usually needs medication to help your bone marrow produce more red blood cells.

Is anemia the same as low iron?

No. Low iron is one cause of anemia, but not the only one. You can have low iron without anemia if your body is still making enough hemoglobin. You can also have anemia from vitamin deficiency, chronic disease, bleeding, or bone marrow problems — none of which involve iron. A blood test can tell you whether your anemia is from iron deficiency or something else.

Can diet alone treat anemia?

Diet can help prevent anemia and support treatment, but usually cannot treat existing anemia on its own. If you have iron deficiency anemia, eating more iron-rich foods helps, but most people also need iron supplements because food alone does not provide enough. If you have B12 deficiency from diet, eating more B12-rich foods or taking supplements helps. For other types of anemia, diet plays a supporting role but medication or other treatment is necessary.

Does anemia mean I have cancer?

No. Anemia has many causes, and cancer is only one of them. Most anemia comes from iron deficiency, vitamin deficiency, or chronic disease. Some people with cancer develop anemia, but most people with anemia do not have cancer. Your doctor will run tests to find out what is causing your anemia.

Can pregnancy cause anemia?

Yes. During pregnancy, your blood volume increases but your red blood cell count does not always keep up, which can lead to anemia. Pregnancy also increases your need for iron and folate. Many pregnant people develop mild anemia, which is usually treated with supplements. Your doctor will check your blood counts during pregnancy and treat anemia if it develops.