You had a blood test, and the form shows hemoglobin above the reference range. The number is alarming, although by itself it does not explain anything yet. Let's look at where high hemoglobin comes from and when it is truly dangerous.
What hemoglobin is considered elevated
Each laboratory prints its own reference range on the form. An elevated result is a number above the upper limit of your laboratory specifically.
The doctor looks not at one line but at the whole picture. They need the red blood cell count and hematocrit — the proportion of blood volume occupied by red blood cells.
In true polycythemia, a hematocrit above 55% occurs in 83% of cases. In secondary erythrocytosis, red blood cells are sometimes 6–8 million per cubic millimeter, sometimes 9 million.
An isolated elevated hemoglobin number is not yet a diagnosis. It may reflect thick blood or ordinary dehydration.
Physiological causes of high hemoglobin
Some cases are not a disease but a reaction of the body.
When fluid is lacking, plasma becomes less, and there are more cells in the same volume. This is how relative polycythemia works in dehydration.
Smoking, excess weight, and a lot of alcohol produce a similar effect. This is apparent erythrocytosis: red blood cells are normal, but there is less plasma. The same happens with diuretics — blood pressure pills that make you run to the toilet more often.
Living in the mountains is a normal adaptation to a lack of oxygen.
Testosterone in high doses also increases red blood cell production. This includes anabolic steroids and replacement therapy for hypogonadism.
Diseases in which hemoglobin is elevated
If everyday causes are ruled out, they look for a condition that increases erythropoietin. This is a kidney hormone; it prompts the bone marrow to produce red blood cells.
Chronic lack of oxygen — COPD, sleep apnea — also raises erythropoietin.
Kidneys: kidney cancer and narrowing of the arteries that supply it can cause high hemoglobin. Sometimes such a result is first found during a routine test for another reason.
This group also includes liver tumors, von Hippel-Lindau disease, and hormone-producing adrenal tumors.
True polycythemia is a rare bone marrow disease. It is a slowly growing blood cancer associated with a change in the JAK2 gene. As a rule, it is not inherited; the average age at diagnosis is 60 years.
High hemoglobin in women and men: are there differences
The list of causes is the same: dehydration, smoking, alcohol, medications, lung and kidney diseases.
The difference is in the frequency of diagnoses. True polycythemia is more common in men and rare in people under 40.
How the cause of the elevation is investigated
They start with a blood test: red blood cells and hematocrit. Then the doctor decides whether a hematologist is needed.
Tests may include:
- a genetic test for a change in the JAK2 gene;
- abdominal ultrasound to look at the kidneys;
- blood chemistry and erythropoietin level;
- blood oxygen saturation and vitamin B12 level;
- bone marrow biopsy.
The set of tests depends on the examination and the first results.
Why high hemoglobin is dangerous and when to see a doctor
Thick blood passes less well through small vessels. This causes headache, dizziness, ringing in the ears, blurred vision, and fatigue.
The skin of the face, hands, and feet reddens. The skin may itch, especially after a warm shower. Sometimes there is heaviness in the left upper abdomen — an enlarged spleen.
The main risk is blood clots. They cause deep vein thrombosis, pulmonary embolism, heart attack, and stroke.
The opposite problems also occur: nosebleeds, bruising, gout with joint pain.
If symptoms persist or recur, see a doctor. They will decide which tests you specifically need.
High hemoglobin by itself is not a reason to call an ambulance. The numbers 103 and 112 are needed for signs of thrombosis: pain, swelling, redness, and tenderness in one leg, hot skin. Also for shortness of breath, chest or between-the-shoulder-blades pain, coughing up blood, or fainting. And for signs of a heart attack or stroke.
This material is for reference and does not replace a doctor's consultation.
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This content is for reference and does not replace a doctor's consultation. Medical disclaimer