Empeiria

Too many red blood cells

Clinically: Polycythaemia · also polycythemia, erythrocytosis, high red blood cell count, high red cells, thick blood, high haematocrit

hematologic MONDO MONDO:0005571 unverified
This describes what this condition typically looks like. It is not a diagnosis and cannot tell you whether you have it -- patterns overlap, results vary between labs, and the same numbers mean different things in different people. Diagnosis usually rests on Hemoglobin, Hematocrit, interpreted alongside symptoms and history rather than read off a report. Note that a normal-looking result does not reliably rule this out -- see the caveats above.

unverified These explanations are written to be easy to read and have not yet been checked against a source. The ranges and measurement notes on this page show theirs.

definition unverified

Your blood has too many red blood cells, which makes it thicker than normal. It can come from a bone marrow disease or be the body's response to something else, such as low oxygen.

An increase in haemoglobin/haematocrit or red cell mass. The WHO 2016 thresholds for polycythaemia vera are haemoglobin 16.5 g/dL / haematocrit 49% in men and 16 g/dL / 48% in women; these levels also trigger haematology referral for erythrocytosis. True (absolute) erythrocytosis must be told apart from relative haemoconcentration.

caveats unverified

Dehydration is the most common cause of a high haematocrit, and it is not true polycythaemia. Living at high altitude can also raise it. In some people the red cell mass is high but the haemoglobin looks normal, because the blood plasma has also increased.

Dehydration is the most common cause of a high haematocrit, and it is not true polycythaemia. Living at high altitude can also raise it. In some people the red cell mass is high but the haemoglobin looks normal, because the blood plasma has also increased.

No clinical version written yet.

The typical lab pattern

What the diagnosis rests on

The results a diagnosis is actually made on.

Hemoglobin high — Diagnostic threshold for polycythaemia vera (WHO 2016): above 16.5 g/dL in men and 16 g/dL in women. The same levels trigger referral for erythrocytosis. It should be confirmed on at least two blood counts.
Hematocrit high — Diagnostic threshold for polycythaemia vera (WHO 2016): above 49% in men and 48% in women. Dehydration is the most common cause of a high haematocrit, so a raised value is not always true polycythaemia.
Consistent with it

Fits the picture, but not enough on its own.

Erythrocyte count high — A higher than normal red cell count can come from polycythaemia vera, low blood oxygen, smoking or dehydration.
Urate high — In polycythaemia vera, the bone-marrow form, uric acid results can be affected, and gout is a possible complication.

How it usually feels

Frequencies say how often a symptom accompanies this condition — not the other way round. Most people with any of these symptoms do not have this.