Increase in red blood cells [RBC] from Testosterone Therapy.

Testosterone replacement therapy sometimes increases hemoglobin and hematocrit with or without an increase the red cell mass.

This condition is often referred to as Polycythemia.

What is Polycythemia?

Polycythemia refers to an increase in the number of red blood cells in the body. The extra cells cause the blood to be thicker, and this, in turn, increases the risk of other health issues, such as blood clots.

Possible symptoms:

It is not uncommon for a person to have polycythemia and be unaware of it. Symptoms tend to build very slowly over time.

Having too many red blood cells thickens the blood, which makes healthy blood flow more difficult. It can also increase a person’s risk of blood clots. This risk is especially high if a person with PV has an excess of both red blood cells and platelets.

A doctor may discover the condition during a routine blood examination or when following up on another condition.

The symptoms of PV may become more apparent over time.

More common symptoms include:

– dizziness or vertigo
– headaches
– excessive sweating
– itchy skin
– ringing in the ears
– blurred vision
– fatigue
– reddish or purplish skin on the palms, earlobes, and nose
– bleeding or bruising
– a burning sensation in the feet
– abdominal fullness
– frequent nosebleeds
– bleeding gums

Without treatment, people with PV may also be more likely to experience complications, such as:

– enlarged spleen
– blood clots
– angina
– stroke
– peptic ulcers
– heart disease
– gout
– other blood disorders, such as myelofibrosis or leukemia

Testosterone dosages should be decreased or possibly discontinued if the hematocrit increases to above 50%. Likewise, clinicians should monitor for the onset of signs and symptoms of polycythemia in these patients, such as ruddy skin, easy bruising, and epistaxis.


Testosterone replacement therapy is the mainstay of treatment for male hypogonadism [also referred to as low testosterone].

Hypogonadism is often associated with declining endogenous testosterone production that occurs as men age. This is sometimes referred to as andropause.

Signs and symptoms of low testosterone include:

  • decreased libido,
  • impotence,
  • decreased body hair,
  • decreased muscle mass,
  • fatigue,
  • and decreased bone mineral density.

Testosterone and other androgens have an erythropoietic stimulating effect that can cause polycythemia, which manifests as an increase in hemoglobin, hematocrit, or red blood cell count.

Polycythemia is an abnormally increased concentration of hemoglobin in the blood, through either reduction of plasma volume or increase in red cell numbers.

Polycythemia is sometimes called erythrocytosis, but the terms are not synonymous because polycythemia refers to any increase in red blood cells, whereas erythrocytosis only refers to a documented increase of red cell mass. The increase in hemoglobin and hematocrit secondary to testosterone use is usually accompanied by an increase in the red blood cell count, which can lead to an increase in blood viscosity. This increase in blood viscosity can reduce cerebral blood flow which could theoretically be a risk factor for thrombosis and stroke. [L]

Polycythemia is also associated with hypertension due to increased blood viscosity and thrombosis. Severe, chronic polycythemia secondary to increased blood viscosity can raise pulmonary arterial pressure and cause increased pulmonary resistance with potential hypoxia, resulting in cor pulmonale.

Thus, increased hemoglobin and hematocrit secondary to testosterone replacement can be significant [L] and in a recent meta-analysis [L] has been cited as the most common side effect of androgen therapy.

The patient with polycythemia on physical exam may present with a ruddy (reddish) complexion, easy bruising, fatigue, and epistaxis. Hematocrit and hemoglobin should be measured before starting testosterone replacement to determine the patient’s baseline. Clearly, if hematocrit is elevated before starting testosterone, the cause should be determined prior to starting androgen therapy. Practice guidelines from the American Association of Clinical Endocrinologists recommend checking hematocrit every 6 months for the first 18 months after starting testosterone, and then check it yearly thereafter if levels remain normal and stable. Testosterone dosages should be decreased or possibly discontinued if the hematocrit increases to over 50%. [L]

Patients with primary polycythemia sometimes receive therapeutic phlebotomy; however, there are no data to support widespread adoption of this practice in testosterone-induced polycythemia. Although this approach seems plausible and may prove beneficial, there are no guidelines for when and how often to perform phlebotomy in this population.

Referenced biomarkers:



Red Blood Cells



Test results may vary depending on your age, gender, health history, the method used for the test, and other things. Your test results may not mean you have a problem. Ask your healthcare provider what your test results mean for you. 

The information on is NOT intended to replace a one-on-one relationship with a qualified health care professional and is not intended as medical advice.

Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s

This site uses Akismet to reduce spam. Learn how your comment data is processed.

%d bloggers like this: