High Hemoglobin: What It Means

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High Hemoglobin: What It Means

By Your Health Magazine Health Information Team

If your Hb is high, your blood contains more hemoglobin than your laboratory’s reference range. Hemoglobin is the oxygen-carrying protein inside red blood cells. A high result may reflect temporary blood concentration from dehydration, the body’s response to low oxygen, a medication effect, or—less commonly—a bone marrow disorder. One abnormal result does not identify the cause, so it should be interpreted with your other blood counts, symptoms, health history, and previous results.

What Does a High Hb Count Mean?

Hb, also written as Hgb, is usually measured as part of a complete blood count. The MedlinePlus hemoglobin test guide explains that reference ranges vary according to factors such as age, sex, and the laboratory performing the test. Altitude can also affect results.

Do not compare your number only with a range found online. Start with the reference interval printed on your laboratory report. A result slightly above that range may have a different significance than a repeatedly or substantially elevated result.

Hemoglobin is related to, but different from, several other CBC measurements:

A high Hb level is not the same as a high MCH. For more context about red blood cell size and hemoglobin content, see what elevated MCV and MCH levels may mean.

Common Reasons Hemoglobin May Be High

Dehydration or reduced plasma volume

Hemoglobin can appear elevated when the liquid portion of the blood is reduced, even if the body has not produced extra red blood cells. Vomiting, diarrhea, heavy sweating, burns, inadequate fluid intake, and certain diuretic medicines may contribute. This is sometimes called relative erythrocytosis or hemoconcentration.

Living at a high altitude

At higher elevations, less oxygen is available in the air. The body may adapt by producing more red blood cells and hemoglobin. A higher Hb count can therefore be expected for some people who live or spend extended periods at high altitude.

Conditions that reduce oxygen

When tissues receive too little oxygen over time, the body may respond by increasing red blood cell production. Possible contributors include:

• Smoking or chronic carbon monoxide exposure
• Chronic lung diseases, including chronic obstructive pulmonary disease
• Certain heart conditions
• Obstructive sleep apnea or other causes of nighttime oxygen loss

Smoking can affect oxygen delivery even when a routine fingertip oxygen reading does not tell the whole story. Loud snoring, witnessed pauses in breathing, morning headaches, or excessive daytime sleepiness may also prompt evaluation for sleep apnea.

Medicines and hormones

Testosterone therapy and erythropoietin or related drugs can raise hemoglobin. Other medicines may also affect red blood cell production. Tell your clinician about prescription medicines, nonprescription products, supplements, hormones, and performance-enhancing substances. Do not stop or change a prescribed treatment based only on a laboratory result.

Polycythemia vera and other uncommon causes

Polycythemia vera is a bone marrow disease in which too many red blood cells are produced; white blood cells and platelets may also be elevated. The National Cancer Institute’s information on polycythemia vera describes how excess blood cells can increase the risk of clotting and other complications. However, a high Hb count alone does not mean that a person has this condition.

Less commonly, kidney disorders or certain tumors can increase production of erythropoietin, the hormone that signals the bone marrow to make red blood cells. These possibilities are considered in context rather than assumed from a single test.

Can High Hemoglobin Cause Symptoms?

A mildly high Hb level often causes no symptoms and is discovered during routine testing. When hemoglobin and red blood cell levels are substantially elevated, symptoms may include:

• Headaches
• Dizziness or lightheadedness
• Blurred or altered vision
• Fatigue or weakness
• Shortness of breath
• Facial redness
• Itching, particularly after a warm bath or shower

These symptoms have many possible causes and cannot confirm why an Hb level is high. Persistent, marked increases in red blood cells may make blood more viscous and contribute to clotting risk, especially when an underlying blood disorder is present.

How a High Hb Result Is Evaluated

Your healthcare professional may first review the entire complete blood count, including hematocrit, red blood cell count, platelets, and white blood cells. The next steps depend on how high the result is, whether it has occurred before, and whether other measurements are abnormal.

Evaluation may include:

1. Confirming the result. A repeat CBC may be appropriate, particularly if dehydration, illness, strenuous activity, or a collection issue could have influenced the first test.
2. Reviewing possible triggers. The clinician may ask about altitude, smoking, sleep symptoms, lung or heart disease, recent fluid loss, and medication use.
3. Checking oxygen status. Pulse oximetry or other testing may be used when low oxygen is suspected.
4. Ordering targeted blood tests. Depending on the pattern, testing may include an erythropoietin level or testing for a JAK2 gene variant associated with polycythemia vera.
5. Considering specialist care. A hematologist may help evaluate an unexplained, persistent, or substantially high Hb count.

Treatment is directed at the cause. Correcting dehydration, addressing an oxygen problem, managing sleep apnea, or medically treating a blood disorder are very different approaches. Do not attempt to lower hemoglobin through blood donation, supplements, or medication changes without professional guidance.

High Hemoglobin Versus Anemia

High hemoglobin generally involves concentrated blood or increased red blood cell production. Anemia involves too little hemoglobin or too few healthy red blood cells to deliver oxygen adequately. Although the findings are opposites, both require interpretation in relation to the rest of the CBC and the person’s health.

When to Seek Care

Contact a primary care clinician if your Hb level remains above the laboratory range, has increased over time, or is accompanied by headaches, dizziness, itching, breathing problems, unusual redness, or vision changes. Evaluation is also appropriate if both hemoglobin and hematocrit are high or if white blood cells or platelets are elevated.

Seek emergency care for sudden chest pain, severe shortness of breath, coughing up blood, fainting, one-sided weakness or numbness, difficulty speaking, a sudden vision change, or a severe unexplained headache. These symptoms can indicate a blood clot, stroke, heart problem, or another emergency regardless of the hemoglobin result.

A high Hb count is a laboratory finding, not a diagnosis. The most useful next step is to review the exact value, reference range, related blood counts, symptoms, medications, and previous results with a qualified healthcare professional.