Hemoglobin in cats and dogs
Hemoglobin is the protein inside red blood cells that carries oxygen. On a complete blood count it is one of three linked numbers, together with hematocrit and the red cell count, that show whether an animal has enough red blood. A low value usually points to anemia; a high one often means the blood is concentrated by dehydration.
What it shows
Each red blood cell is about one-third hemoglobin. The analyzer breaks the cells open and measures how much hemoglobin is in a given volume of blood. Because that share is so stable, hemoglobin moves together with the hematocrit (the part of blood volume taken up by red cells) and the red cell count: as a rough rule, hematocrit in percent is about three times hemoglobin in g/dL.
In dogs and cats vets usually lean on hematocrit or PCV (packed cell volume — the share of red cells measured by spinning blood in a tube) rather than on hemoglobin, because hemoglobin is easier to distort: fatty (lipemic) plasma and some changes in red cells make the measured value falsely high. When all three numbers agree, the picture is clear; when hemoglobin disagrees with the other two, a sample problem is the first suspect.
Higher than reference — what it may be a sign of
- Dehydration — a frequent reason. The blood loses water, so red cells become relatively concentrated: after vomiting, diarrhoea or not drinking enough.
- Breed: greyhounds and other sighthounds normally have more red cells; eClinPath gives an average hematocrit of about 59% in adult greyhounds.
- Erythrocytosis: the body really makes too many red cells — driven by the hormone erythropoietin, or, rarely, as a bone marrow disorder (polycythemia vera).
- Sample artefacts: lipemia (for example, blood taken soon after a meal), Heinz bodies (clumps of damaged hemoglobin inside red cells) in cats, or hemoglobin-based oxygen carriers given in a clinic can make the measured value falsely high.
Lower than reference
A low hemoglobin is the core of anemia. Vets sort anemia by mechanism:
- Blood loss: injury, bleeding tumours, stomach ulcers or bleeding in the gut (black stools), parasites such as fleas, ticks and hookworms.
- Destruction of red cells (hemolysis): immune-mediated hemolytic anemia, blood parasites such as Mycoplasma haemofelis in cats or Babesia in dogs, toxins such as onion, zinc or paracetamol.
- Too little production: chronic kidney disease (the kidneys make erythropoietin), chronic inflammation, bone marrow disease, FeLV (feline leukemia virus) in cats.
After blood loss or hemolysis the marrow usually answers with young red cells (reticulocytes) — the anemia is regenerative; when production fails, it is not. A temporary dip can also follow intravenous fluids or sedation.
Look at together with
- Hematocrit (HCT/PCV) and red cell count (RBC) — the other two members of the trio.
- Reticulocytes — show whether the marrow is responding: high after blood loss and hemolysis, low when production fails.
- MCV, MCH, MCHC — size of red cells and how much hemoglobin each carries.
- Creatinine and SDMA — a non-regenerative anemia in an older animal raises the question of kidney disease.
Units and conversion
Hemoglobin is reported in g/L (the SI unit, common in Europe) or in g/dL (common in North America and on many analyzers). 1 g/dL equals 10 g/L, so 12 g/dL is 120 g/L. In the app each row keeps the unit printed on the form, and the chart converts everything to one unit so results from different labs line up.
Reference range
The reference range is on your lab’s form. It differs between species, breeds and analyzers. Dehydration can hide anemia: in a dehydrated anemic animal hemoglobin and hematocrit can still sit inside the range, and the drop shows only once fluids are restored. That is why a vet reads hemoglobin together with the animal’s hydration and the rest of the blood count, and why a series of tests says more than one result.
Cats and dogs
In cats anemia is often first noticed as lethargy or pale gums, and a cat whose anemia develops slowly can look almost normal at home because it adapts. Typical feline causes are fleas (especially in kittens), Mycoplasma haemofelis, FeLV, toxins such as onion or paracetamol, and chronic kidney disease — according to the Cornell Feline Health Center, 30–65% of cats with advancing CKD develop some degree of anemia.
In dogs breed shifts the picture most: greyhounds, whippets and other sighthounds have higher hematocrit and hemoglobin with healthy blood. Common causes of anemia in dogs include bleeding, immune-mediated hemolytic anemia, infections such as Babesia and Ehrlichia, and long-term kidney disease, which reduces red cell production.
Add a lab form — Pet Tracker Space recognises the lines, keeps the form’s units and draws each indicator over time with your lab’s reference band.
Sources
This page explains what a lab value means. It is not a diagnosis and not a substitute for your veterinarian — only they can interpret results for your pet.