Anemia is a condition in which the number of red blood cells circulating in your bloodstream is lower than usual.

Red blood cells carry oxygen from your lungs to your other organs. If you have anemia, your organs might receive less oxygen. When your brain gets less oxygen than usual, you might experience headaches.

Several types of anemia can cause headaches.

Iron deficiency anemia

Iron deficiency anemia (IDA) can cause the brain to receive less oxygen than it needs to function optimally, leading to basic headaches.

IDA has also been associated with migraine, especially in women who are menstruating.

Anemia due to vitamin deficiency

Like a lack of iron, low levels of some vitamins, such as B-12 and folate, can cause anemia. These types of anemia also result in reduced oxygen levels in the brain, which can cause basic headaches.

Sickle cell anemia and thalassemia

Sickle cell anemia and thalassemia are types of anemia that cause red blood cells to become stickier and form clots or to form an abnormal shape. These conditions can also lead to headaches.

Anemia is a risk factor for developing cerebral venous thrombosis (CVT), a rare condition in which a blood clot forms in a vein in the brain. This condition may also be called cerebral sinus venous thrombosis (CSVT).

Basic headaches

This is the type of headache most people get from time to time. A variety of factors can cause these headaches, including low levels of oxygen in your brain.

Migraine attacks

Migraine pain varies, but it is often described as a throbbing sensation on one side of the head. Migraine attacks occur regularly and may have associated symptoms such as changes in your vision or sensitivity to light or sound. They are often severe and long-lasting.

CVT headaches

CVT is a blood clot that develops in a vein that drains blood from your brain. The blockage can cause blood to back up, and the resulting distension of the vein walls, inflammation, and leakage of blood into your brain causes a headache.

Headaches are the most common symptom of CVT, and they occur in about 90 percent of people with the condition.

Headaches from IDA

If the symptoms that accompany your headache seem to indicate you have IDA, your doctor can perform blood tests to determine how many red blood cells and how much iron you have.

Your doctor may also do tests to determine if your IDA is the result of blood loss, such as through heavy menstrual flow or blood in your stool.

Headaches from vitamin deficiency

As with IDA, your doctor can do blood tests to determine your levels of B-12, folate, and other vitamins, which may be contributing to low numbers of red blood cells.

Headaches from CVT

If you have CVT, you may experience other neurologic symptoms besides headaches. However, up to 40 percent of the time, there aren’t any other symptoms, which can make it harder to diagnose.

The initial test is a CT scan. Your doctor will look for specific things that point to a diagnosis of CVT. An MRI can show the actual clot in the vein, but it can also look normal about 30 percent of the time.

Other, more invasive tests can be used to confirm the diagnosis if it’s not clear from a CT scan and an MRI.

Basic headaches from IDA

Headaches caused by IDA are treated by increasing your iron level with iron pills. Once your iron level is back to normal, your red blood cells will be able to carry the proper amount of oxygen to your brain.

Basic headaches from vitamin deficiencies

Replenishing the vitamins that are at low levels in your body will increase the number of red blood cells and the amount of oxygen delivered to your brain.

Migraine attacks

Whether or not they are related to IDA, migraine attacks are usually treated with medications called triptans. These medications work on brain chemicals such as serotonin and are a very effective treatment.


Once seizures and other neurologic symptoms have been stabilized, CVT is almost always treated with anticoagulants, also known as blood thinners, to dissolve the blood clot. Occasionally, surgery is necessary to remove the clot.

See your doctor whenever you have a headache that is unusual for you and doesn’t feel like a typical headache. Also let your doctor know if you have your first migraine attack or any migraine attacks that differ from your usual ones.

seek emergency care for CVT

CVT is a medical emergency that should be evaluated right away. Things to look for include:

  • a particularly severe headache
  • stroke-like symptoms such as facial paralysis or loss of sensation or mobility in an arm or leg
  • vision changes, especially associated with dizziness or vomiting, which can be a sign of brain swelling (papilledema)
  • confusion or loss of consciousness
  • seizures

Several types of anemia can cause headaches. A deficiency of iron or vitamins can lead to headaches related to low oxygen levels in the brain. IDA has also been shown to play a role in migraine, especially during menstruation.

A rare cause of headaches called CVT is seen in people with conditions that cause their red blood cells to form clots.

All these conditions can be treated fairly easily if diagnosed promptly.