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High Hemoglobin Symptoms: Causes, Signs & What to Do

High hemoglobin means your blood carries more of the oxygen-carrying protein than your lab range. Learn what a high result means, the symptoms, common causes such as dehydration, smoking, sleep apnea, and testosterone, how it relates to hematocrit, and which tests come next.

Published

April 23, 2026

Last updated

November 4, 2026

Read time

9 min read

Medically reviewed by

Rhonda Collins, FNP-C

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High hemoglobin means your blood has more of the oxygen-carrying protein than the reference range on your lab report. MedlinePlus lists common adult ranges of 13.8 to 17.2 g/dL for men and 12.1 to 15.1 g/dL for women, and the exact range varies slightly between labs ^[1]. A single, mildly high result is often not a sign of disease: dehydration, smoking, and living at a higher altitude can all raise hemoglobin ^[1][2]. Because dehydration alone can push the number up, a mildly high result is usually rechecked with a repeat complete blood count (CBC) once you are well hydrated. A result that stays high needs a cause, which can range from smoking, sleep apnea, or testosterone therapy to the bone marrow disorder polycythemia vera ^[2][3]. See the Hemoglobin biomarker overview for how it relates to hematocrit and RBC indices.

What High Hemoglobin Means

Hemoglobin is an iron-rich protein in red blood cells that carries oxygen from the lungs to the rest of the body ^[2]. Merck Manual considers any hemoglobin or hematocrit above the normal values for age and sex to be erythrocytosis, meaning too many red blood cells ^[3]. A high level happens in one of two ways:

• The body makes more red blood cells. This is a true rise, usually driven by low oxygen levels over a long period, by hormones or medicines, or by a bone marrow disorder ^[1][3].
• The blood has less fluid. Dehydration, diarrhea, burns, or diuretics shrink the plasma, so the same red cells are more concentrated. Merck Manual calls this spurious erythrocytosis ^[3].

A hemoglobin result cannot tell you which of these is happening. MedlinePlus notes that the test cannot show the cause of an abnormal level, so your symptoms, medical history, and other blood results are read alongside it ^[2].

Symptoms of High Hemoglobin

Many people with high hemoglobin have no symptoms, and the result is found on a routine CBC. Merck Manual notes that secondary erythrocytosis may cause no symptoms, and that polycythemia vera is often symptom-free at first ^[3][4]. When symptoms appear, they mostly come from thicker blood:

• headache;
• dizziness or lightheadedness;
• blurred vision or other visual disturbances;
• a red or flushed face (plethora);
• fatigue and weakness;
• shortness of breath; and
• red, warm, painful hands and feet (erythromelalgia) ^[3][4].

Symptoms that point more toward polycythemia vera include itching after a hot bath or shower (aquagenic pruritus), which Merck Manual says may be the earliest symptom, and a full feeling in the upper left abdomen from an enlarged spleen ^[4][5]. MedlinePlus also lists ringing in the ears, joint pain, and trouble breathing when lying down ^[5].

When low oxygen is the cause, symptoms of the underlying condition often stand out: shortness of breath from lung disease, or a bluish tint to the skin (cyanosis) ^[3]. Sleep apnea, a disorder in which breathing repeatedly stops during sleep, is another cause of high hemoglobin ^[2].

Thicker blood raises the risk of blood clots. Get urgent care for sudden weakness or trouble speaking, chest pain, a painful swollen leg, or sudden vision loss, which can signal a stroke, heart attack, deep vein thrombosis, or a clot in the eye ^[4].

Symptoms of high hemoglobin in women

Women have the same symptoms as men, but the threshold for a high result is lower: above 15.1 g/dL at many labs, compared with 17.2 g/dL for men ^[1]. Men develop polycythemia vera more often than women ^[6]. When women do develop it, Merck Manual notes that it can appear much earlier, in their 20s or 30s, often as a blood clot in the veins that drain the liver (Budd-Chiari syndrome) ^[4]. In polycythemia vera, a rise in plasma volume can also keep the hematocrit in the normal range, which Merck Manual says is particularly the case in women ^[4].

What Causes High Hemoglobin

MedlinePlus says a high hemoglobin level is most often caused by low oxygen levels in the blood over a long period ^[1]. The causes fall into a few groups.

Less fluid in the blood (relative or spurious erythrocytosis):

• dehydration, for example from severe diarrhea ^[1];
• burns ^[3]; and
• diuretics (water pills) ^[3].

Low oxygen levels that drive more red cell production:

• smoking, which raises carbon monoxide-bound hemoglobin (carboxyhemoglobin) ^[1][3];
• lung disease, including scarring of the lungs (pulmonary fibrosis) ^[1][2];
• sleep apnea ^[2];
• heart disease, including heart problems present from birth (congenital heart disease) and failure of the right side of the heart ^[1][2]; and
• living at, or recently moving to, a higher altitude ^[1][3].

Medicines and hormones:

• testosterone and other androgenic steroids ^[3];
• erythropoietin (EPO) taken as a medicine or for performance enhancement ^[3];
• sodium-glucose cotransporter-2 (SGLT-2) inhibitors, a class of diabetes medicines ^[3]; and
• some tyrosine kinase inhibitors used in cancer treatment ^[3].

Tumors and rare inherited causes:

• tumors that release EPO, such as kidney tumors (renal cell carcinoma) ^[1][3]; and
• rare inherited conditions, such as hemoglobin variants that hold oxygen too tightly ^[3].

Bone marrow overproduction:

• polycythemia vera, in which a mutation in the JAK2 gene makes the bone marrow produce red cells independently of EPO. The JAK2 V617F mutation is present in about 90% of people with polycythemia vera ^[4].

High Hemoglobin and Hematocrit Together

High hemoglobin and high hematocrit usually appear together, because both rise when there are more red blood cells. Hemoglobin measures the oxygen-carrying protein, while hematocrit measures the share of your blood volume taken up by red blood cells. StatPearls notes that elevated hemoglobin or hematocrit is how doctors recognize an increased red cell mass, and that current practice relies on these two values for diagnosis ^[7]. The diagnostic criteria for polycythemia vera use both: a JAK2 mutation with hemoglobin above 16.5 g/dL or hematocrit above 49% in men, or hemoglobin above 16.0 g/dL or hematocrit above 48% in women ^[8].

The two values can also disagree. Merck Manual notes that in polycythemia vera, hemoglobin can be normal when iron deficiency is also present, even while the red cell count is high, and that the red cell count is the most useful measure of erythrocytosis ^[4]. That is why the whole CBC is read together rather than one number alone.

For more on each result, see high hematocrit symptoms and high red blood cell count symptoms. The hemoglobin vs RBC comparison explains how hemoglobin and the red cell count differ.

Can Dehydration Cause High Hemoglobin?

Yes. MedlinePlus lists dehydration, for example from severe diarrhea, as a cause of high hemoglobin ^[1]. Merck Manual describes this as spurious erythrocytosis: the plasma shrinks from fluid loss, burns, or diuretic use, so the red cells are more concentrated even though the body is not making more of them ^[3]. Because the red cell mass has not actually increased, a repeat CBC once you are well hydrated is the usual first step to tell dehydration apart from a true rise.

Is 17.5 Hemoglobin High?

Yes, 17.5 g/dL is above the common adult range for both sexes. For a man it is just above the MedlinePlus upper limit of 17.2 g/dL, and for a woman it is well above the upper limit of 15.1 g/dL ^[1]. It is also above the hemoglobin levels used in the polycythemia vera criteria, 16.5 g/dL for men and 16.0 g/dL for women, but those criteria also require a JAK2 mutation ^[8].

Context matters. StatPearls notes that reference values vary with altitude, ethnicity, and country, and gives 16 g/dL, plus or minus 2 g/dL, as a reference value for a healthy adult man ^[7]. A man with 17.5 g/dL who smokes, takes testosterone, or was dehydrated at the draw has common explanations to check first ^[1][3]. A repeat CBC shows whether the result is persistent.

How Is High Hemoglobin Lowered?

High hemoglobin is lowered by treating its cause ^[3]. What that looks like depends on the cause:

• Dehydration: restoring fluid. A repeat CBC once you are well hydrated shows whether the result was spurious.
• Smoking: stopping. Merck Manual notes that smoking-related erythrocytosis is reversible and that levels normalize after quitting ^[3].
• Low oxygen from lung disease or other conditions: treating the condition, sometimes with oxygen therapy ^[3].
• Testosterone therapy: the Endocrine Society guideline recommends monitoring hematocrit during treatment ^[9]. A urology consultation guide advises that prescribers decrease or stop testosterone if hematocrit rises above 54% until it normalizes ^[10]. Do not change a prescription on your own.
• EPO-producing tumors: Merck Manual notes that removing the lesion is curative ^[3].
• Polycythemia vera: regular phlebotomy, which removes blood, usually with low-dose aspirin ^[4][8]. Merck Manual gives phlebotomy targets of a hematocrit below 45% in men and below 42% in women ^[4]. Medicines that reduce blood cell production are added for higher-risk disease ^[8].

For secondary causes, Merck Manual notes that phlebotomy is rarely needed and is limited to relieving symptoms, because the higher hemoglobin can be the body’s response to low oxygen ^[3].

Normal Hemoglobin Levels

The reference ranges come from MedlinePlus, which notes that normal ranges vary slightly among laboratories ^[1]. Use the range printed on your own report. The polycythemia vera levels come from a 2024 review of the diagnostic criteria ^[8]. They are one part of a diagnosis that also needs a JAK2 mutation, so a man’s result between 16.5 and 17.2 g/dL is not a sign of polycythemia vera on its own.

When to See Your Care Team

Book a 1:1 consultation with a Mito clinician if your hemoglobin stays above your lab’s range on a repeat CBC taken when you are well hydrated, or sooner if you have symptoms such as headaches, vision changes, or itching after a warm shower. Bring a list of your medicines, including testosterone or SGLT-2 inhibitors, and mention smoking and any snoring or pauses in breathing at night.

If the cause is still unclear, the next steps are tests your clinician orders. A serum erythropoietin (EPO) level helps separate the causes: it is usually low in polycythemia vera, and elevated or inappropriately normal when low oxygen or a tumor is driving red cell production ^[3][4]. JAK2 mutation testing follows when polycythemia vera is suspected ^[4][8]. If your clinician recommends it, Mito offers an erythropoietin (EPO) blood test.

References

1. MedlinePlus Medical Encyclopedia: Hemoglobin
2. MedlinePlus: Hemoglobin Test
3. Merck Manual Professional Version: Secondary Erythrocytosis
4. Merck Manual Professional Version: Polycythemia Vera
5. MedlinePlus Medical Encyclopedia: Polycythemia vera
6. MedlinePlus Genetics: Polycythemia vera
7. Pillai AA, Kaur A, Mukkamalla SKR. Polycythemia. StatPearls (PubMed record)
8. Tefferi A, Barbui T. Polycythemia vera: 2024 update on diagnosis, risk-stratification, and management. Am J Hematol (PubMed record)
9. Bhasin S, et al. Testosterone Therapy in Men With Hypogonadism: An Endocrine Society Clinical Practice Guideline (PubMed record)
10. Agrawal P, Singh SM, Kohn T. Management of Erythrocytosis in Men Receiving Testosterone Therapy: Clinical Consultation Guide. Eur Urol Focus (PubMed record)

Related Resources

• Hemoglobin biomarker overview
• Low Hemoglobin Symptoms: Causes, Signs & What to Do
• How to Improve Your Hemoglobin Naturally
• Hemoglobin vs RBC: Key Differences Explained
• Hemoglobin vs WBC: Key Differences Explained
• High Hematocrit Symptoms
• High Red Blood Cell Count Symptoms

Frequently asked questions

Can smoking cause high hemoglobin?

Yes. Smoking raises the amount of carboxyhemoglobin in the blood, which is hemoglobin bound to carbon monoxide. Merck Manual explains that this causes tissue hypoxia, which drives the body to make more red blood cells, and that smokers usually also have a lower plasma volume, which concentrates the blood. The rise is reversible: Merck Manual notes that levels normalize after quitting smoking.

What is polycythemia vera, and what are its hemoglobin diagnostic criteria?

Polycythemia vera (PV) is a bone marrow disorder that makes too many red blood cells, often with high white cells and platelets too. A 2024 review in the American Journal of Hematology describes a working diagnosis as a JAK2 mutation together with hemoglobin above 16.5 g/dL or hematocrit above 49% in men, or hemoglobin above 16.0 g/dL or hematocrit above 48% in women. A bone marrow exam is advised but not required. Merck Manual notes that the erythropoietin (EPO) level is usually low. Treatment centers on regular phlebotomy to keep hematocrit below 45%, usually with low-dose aspirin.

Does high hemoglobin mean I am "over-oxygenated"?

No. High hemoglobin means there are more red blood cells and hemoglobin in circulation, but the extra cells make the blood thicker. MedlinePlus explains that in polycythemia vera this thicker blood cannot flow through small blood vessels normally, which causes symptoms such as headache, dizziness, and vision problems. That is why a very high level from polycythemia vera is treated by lowering it, not by keeping it high.

Is high hemoglobin always from a serious cause?

No. MedlinePlus notes that an abnormal hemoglobin result does not always mean a condition that needs treatment, and that dehydration, smoking, and living at a higher altitude can raise it. Conditions such as lung disease and sleep apnea are more significant causes that are worth finding. Polycythemia vera, the main primary bone marrow cause, is uncommon: Merck Manual estimates its incidence in the United States at about 2 per 100,000 people a year.

What should I not eat if my hemoglobin is high?

The medical sources used on this page do not recommend avoiding any specific food to lower a high hemoglobin. MedlinePlus lists diet as one factor that can affect a result, alongside dehydration and smoking, but high hemoglobin is lowered by treating its cause. Correcting dehydration and stopping smoking are the everyday changes these sources connect to it.