What Causes High or Low Hemoglobin Levels?

Maintaining normal hemoglobin levels is important, as this blood protein carries oxygen to your cells. In males, a healthy hemoglobin level is between 13.2 and 16.6 grams per deciliter of blood (g/dL). In females, a hemoglobin count of between 11.6 and 15 g/dL is considered normal and healthy.

A lower-than-normal hemoglobin count means that your cells are not getting enough oxygen from your blood. Without ample oxygen, cells cannot convert glucose (the body's main fuel source) into energy, leading fatigue, weakness, and other signs of anemia.

By contrast, a high-than-normal hemoglobin count means that your body is being deprived of oxygen due to conditions like smoking, living at high altitudes, having a heart or lung disease, or having a bone marrow disease that causes the overproduction of red blood cells.

This article describes the various causes and symptoms of high and low hemoglobin levels and how each are treated.

High Hemoglobin Levels

A hemoglobin level above 17.5 for males and 15.5 for females is considered high. That can be due to a variety of causes.

Causes

Your cells need oxygen to survive. Your body may make excess hemoglobin at times when it's struggling to get enough oxygen to your cells. More hemoglobin leads to better oxygen delivery.

You can also have a high hemoglobin level if your body makes too many red blood cells. It may do that due to disease. Some diseases trigger the extra production themselves, while some cause low levels that your body may try to compensate for.

High hemoglobin levels can also be caused by:

• Polycythemia vera (a condition that increases levels of all blood cells)
• Heart or lung disease 
• Liver or kidney cancer 
• Chronically low oxygen levels 
• Smoking cigarettes

Being in a high-altitude location can raise your hemoglobin level temporarily until you get back to a lower elevation or until your body adjusts to the atmospheric pressure at a high elevation.

Symptoms

Generally, a high hemoglobin level doesn't cause any symptoms. However, it can lead to some serious, potentially life-threatening complications. These include:

• Blood clots
• Heart attack
• Stroke

Treatment

The treatment for high hemoglobin levels depends on what's causing it. If it's caused by a disease, treating that disease should help lower levels.

That may mean:

• Medications for polycythemia vera 
• Medications or surgery for heart disease
• Oxygen supplementation, medications, or surgery for lung disease
• Cancer treatment
• Smoking cessation
  
• Fluids and electrolytes for dehydration 

In some situations, you may need a blood transfusion to give your body enough red blood cells. This can be a one-time treatment in situations that cause a temporary increase in hemoglobin levels. For chronic conditions, you may need periodic transfusions.

Low Hemoglobin Level

A hemoglobin level below the normal value (13.5 for males, 12 for females) is considered low. Usually, a low hemoglobin level is a sign of iron deficiency anemia.

Causes and Risk Factors

You can develop a low hemoglobin level if you don’t make enough red blood cells or if you lose them faster than your body can replenish them.

Low hemoglobin levels are caused by: 

• Low dietary iron or impaired iron absorption 
• Menstrual bleeding
• Blood loss from any cause, including surgery, trauma, or a gastrointestinal (stomach) bleed from an ulcer 
• Cancer, especially leukemia (blood-cell cancers) 
• Chemotherapy
  

Symptoms

A low hemoglobin level commonly causes noticeable symptoms. They include: 

• Low energy 
• Sleepiness
• Pale skin 
• Headaches 
• Dizziness

Very low hemoglobin can cause:

• Tachycardia (rapid heart rate)
• Hypotension (low blood pressure)
• Dyspnea (trouble breathing)
  

Treatment

Treatment for a low hemoglobin level depends on the cause. It may include: 

• Increasing iron in your diet through foods and/or supplements 
• Treating a bleeding ulcer to prevent recurrent blood loss 
• Cancer treatment
• Supplemental erythropoietin (EPO, a hormone in the kidneys that helps produce red blood cells)
• Treatments that stimulate bone marrow to raise red blood cell production 

If you're being treated with chemotherapy or another medication that causes low hemoglobin levels, you'll probably need to stay on the medication, but also have treatments to increase hemoglobin production.

Summary 

Your hemoglobin level reflects the number of red blood cells in your body and how efficiently they carry oxygen to your cells. This protein contains iron, which can be measured with a blood test.

Many things cause low or high hemoglobin, and they produce a variety of symptoms. Usually, the symptoms of low hemoglobin are more noticeable than symptoms of high hemoglobin and can lead to complications.

Most causes of hemoglobin abnormalities can be treated with medication. Sometimes a blood transfusion is necessary to correct very low hemoglobin levels. 

A Word From Verywell 

Hemoglobin is an important protein in your blood that can be measured with a simple blood test. Your hemoglobin level reflects the health of your red blood cells and how well your body can get oxygen.

If your hemoglobin level is too high or too low, you should not ignore it. Your medical team can find the cause and recommend treatments to reduce symptoms and prevent complications.