Causes of Abnormal Hemoglobin Level (2024)

Blood Disorders

Many different conditions can cause hemoglobin abnormalities

ByHeidi Moawad, MD

Updated on January 11, 2024

Medically reviewed byYasmine S. Ali, MD, MSCI

Fact checked byNick Blackmer

Table of Contents

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Table of Contents

  • Testing Levels

  • High Levels

  • Low Levels

  • FAQ

Maintaining normal hemoglobin levels is important, as this blood protein carries oxygen to your cells. There can be slight variations between what different healthcare providers consider “healthy,” but in general, a healthy hemoglobin level for males aged 19–65 years is between 13.1 and 17.5 grams per deciliter of blood (g/dL). In adult females aged 19–65 years, a hemoglobin count of between 10.6 and 15.6 g/dL is typically considered normal and healthy. See table for more detail.

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 to fatigue, weakness, and other signs of anemia.

By contrast, a higher-than-normal hemoglobin count means that your body is being deprived of oxygen. This can be due to conditions like smoking, living at a high altitude, 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 is treated.

How Are Hemoglobin Levels Tested?

A hemoglobin test measures the amount of hemoglobin in your blood. The test requires a simple blood draw.

Your hemoglobin is typically tested as a part of a complete blood count (CBC). You don’t usually need to do anything to prepare for this test unless your healthcare provider has also ordered other tests to be done on the same blood sample. Make sure to ask your provider if you should fast before you arrive for the test.

A blood draw is done through a needle inserted into a vein in your arm. You will feel a small prick or sting and you may have bruising and soreness afterwards.

Factors That Affect Results

Several factors can affect your hemoglobin test results, including:

  • Your age and sex
  • Your posture while blood is being drawn
  • Environmental conditions, such as temperature, humidity, and air pollution
  • Intense exercise within 24 hours before testing

If your healthcare provider orders a blood test for you, ask them if there is anything you should or should not do leading up to your test. For the most accurate results, follow their directions carefully.

Complete Blood Count (CBC) Normals and Abnormals

Normal Hemoglobin Levels by Age/Sex
Males 1 to 5 years10.7 to 14.2 g/dL
Females 1 to 5 years11 to 14.2 g/dL
Males 6 to 18 years11.9 to 16.9 g/dL
Females 6 to 18 years11.2 to 15.1 g/dL
Males 19 to 6513.1 to 17.5 g/dL
Females 19 to 6510.6 to 15.6 g/dL
Males 66+11.4 to 17.1 g/dL
Females 66+10.9 to 15.9 g/dL

High Hemoglobin Levels

A hemoglobin level above the normal value is considered high. That can be due to a variety of causes.

Causes and Risk Factors

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, kidney, or lung disease
  • Chronically low oxygen levels
  • Dehydration
  • Smokingtobacco
  • Liver or kidney cancer

Your hemoglobin levels can also increase temporarily while you are in a high-altitude location. This will resolve on its own when you get back to a lower elevation or when your body adjusts to the atmospheric pressure at a high elevation.


You can test high for hemoglobin levels if you’re dehydrated, but that’s only because your blood contains less water. Once you’re hydrated, the number should go back to normal.


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


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.

How Can You Increase Your Red Blood Cells?

Low Hemoglobin Levels

A hemoglobin level below the normal value is considered low.Usually, a low hemoglobin level is a sign of iron deficiency anemia.

Causesand 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
  • Cancer, especially leukemia (blood-cell cancers)
  • Chemotherapy
  • Blood loss from any cause, including surgery, trauma, or a gastrointestinal (stomach) bleed from an ulcer

Excess Fluid

You can have low hemoglobin levels if your blood contains excess fluid (the opposite of dehydration.) That can be caused by some medical conditions, especially kidney failure.


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 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.

What Is Anemia?

Anemia is a low red blood cell count or diminished red blood cell function. Many things cause anemia, including low iron in the diet.

The Different Types of Anemia


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.

Frequently Asked Questions

  • What is a critical hemoglobin level?

    Hemoglobin levels below 5.0 g/dL can lead to heart failure and death. Hemoglobin levels above 20 g/dL can lead to blood clots. If a lab technician detects a critical hemoglobin level, they will notify the patient’s healthcare providers immediately.

  • Can certain foods help regulate your hemoglobin count?

    If you have mild iron deficiency anemia, you can sometimes normalize your normal hemoglobin level by eating enough foods that contain iron:

    • Red meat
    • Shellfish
    • Beans
    • Spinach
    • Kale
    • Fortified grains

    Learn MoreThe 7 Best Iron Supplements

  • How can I prevent irregular hemoglobin levels?

    The best way is to not smoke cigarettes. Smoking itself raises levels, plus it increases your risk of chronic lung disease, heart disease, and cancer, which also raise hemoglobin levels.

    To prevent low hemoglobin levels, be sure to get enough iron in your diet.

    Learn MoreHow to Successfully Quit Smoking

12 Sources

Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.

  1. Centers for Disease Control and Prevention. National Health and Nutrition Examination Survey 2021 laboratory procedures manual.

  2. Neufeld LM, Larson LM, Kurpad A, Mburu S, Martorell R, Brown KH. Hemoglobin concentration and anemia diagnosis in venous and capillary blood: biological basis and policy implications. Ann N Y Acad Sci. 2019;1450(1):172-89. doi:10.1111/nyas.14139

  3. De la Salle B. Pre- and postanalytical errors in haematology. Int J Lab Hematol. 2019;41(1):170-176. doi:10.1111/ijlh.13007

  4. National Library of Medicine: MedlinePlus. CBC blood test.

  5. Dana-Farber Cancer Institute. Hemoglobin and cancer: what’s the connection?.

  6. Lee AJ, Kim SG, Nam JY, Yun J, Ryoo HM, Bae SH. Clinical features and outcomes of JAK2 V617F-positive polycythemia vera and essential thrombocythemia according to the JAK2 V617F allele burden. Blood Res. 2021;56(4):259-265. doi:10.5045/br.2021.2021089

  7. Tabasi S, Parkhideh S, Roshandel E, et al. The association of disease type, pre-transplant hemoglobin level and platelet count with transfusion requirement after autologous hematopoietic stem cell transplantation. Caspian J Intern Med. 2021;12(4):544-550. doi:10.22088/cjim.12.4.544

  8. Nakamori E, Shigematsu K, Higashi M, Yamaura K. Postoperative noninvasive hemoglobin monitoring is useful to prevent unnoticed postoperative anemia and inappropriate blood transfusion in patients undergoing total hip or knee arthroplasty: A randomized controlled trial. Geriatr Orthop Surg Rehabil. 2021;12:21514593211060575. doi:10.1177/21514593211060575

  9. National Heart, Lung, and Blood Institute. Anemia: symptoms.

  10. Phillips J, Henderson AC. Hemolytic anemia: evaluation and differential diagnosis. Am Fam Physician. 2018;98(6):354-361.

  11. National Heart, Lung, and Blood Institute. Your guide to anemia.

  12. Hemoglobin level, Nurs Crit Care. 2020;15(4):34-35. doi:10.1097/01.CCN.0000660408.76985.53

Causes of Abnormal Hemoglobin Level (2)

By Heidi Moawad, MD
Dr. Moawad is a neurologist and expert in brain health. She regularly writes and edits health content for medical books and publications.

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Causes of Abnormal Hemoglobin Level (2024)


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