Albumin in cats and dogs

What it shows

Albumin makes up about 35–50% of plasma protein (eClinPath) and provides about 80% of the plasma’s water-holding, or colloid osmotic, effect (Merck). It binds unconjugated bilirubin, fatty acids, calcium, magnesium, zinc, copper and many drugs, and acts as an antioxidant. The liver does not store albumin but makes it continuously, using only about a third of its capacity in health. In dogs its half-life is estimated at about 8 days (Merck).

Albumin is also a negative acute-phase protein: during inflammation, signalling molecules make the liver produce less of it. So a low albumin is not automatically about the liver.

Higher than reference — what it may be a sign of

• Dehydration — the most common cause: albumin rises because water is lost, not because more is made (eClinPath).
• Corticosteroids — in a small study in Beagles prednisolone raised albumin by 15–17%, probably through fluid shifts.
• Isolated reports in dogs — some Scottish terriers with adrenal dysfunction, and a dog with a liver tumour.
• Sample — heparin plasma can read higher than serum, because the dye also binds other proteins.

Lower than reference

Low albumin has three groups of causes (eClinPath, VCA):

• Made too little: liver failure — eClinPath notes that low albumin appears when more than 80% of functional liver mass is lost; inflammation; long-term lack of protein in food; in dogs also Addison’s disease (VCA).
• Lost: through the kidneys (protein-losing nephropathy), the gut (protein-losing enteropathy), bleeding, or severe oozing skin lesions and burns.
• Moved out or diluted: into the abdomen or chest with effusions, or diluted by excess drip fluids.

Very low albumin lets fluid leak out of vessels: swelling of the legs and over the sternum, fluid in the abdomen or around the lungs (VCA).

Look at together with

• Globulin and A/G ratio — gut loss, bleeding and skin loss usually take both groups, keeping the ratio near usual; kidney loss takes albumin while globulins are kept, so the ratio falls (eClinPath).
• UPC — protein loss in urine; Merck uses a UPC above 3 with high cholesterol to point to protein-losing nephropathy.
• Cholesterol — often low with gut protein loss and liver failure, high with nephrotic syndrome.
• Bile acids — check liver function when albumin is low without another explanation (VCA).

Units and conversion

Albumin is reported in g/L (г/л) or g/dL (г/дл); one g/dL equals 10 g/L, so 3.0 g/dL is 30 g/L. Veterinary labs measure albumin with the dye bromocresol green. Another dye, bromocresol purple, widely used in human labs, gives falsely low values in animal serum and is not used for animal samples (eClinPath).

Reference range

The reference range is on your lab’s form. Very young animals tend to have lower values: kittens up to about 2 weeks, puppies up to 6–20 weeks, though puppies often remain within adult ranges (eClinPath). In a sick animal an early fall in albumin can reflect inflammation; a steady fall over several tests prompts a search for where albumin is going.

Cats and dogs

Sources

1. eClinPath (Cornell University) — Albumin
2. Miscellaneous Serum Biochemical Measures in Hepatic Disease in Small Animals. Merck Veterinary Manual
3. VCA Animal Hospitals — Low Albumin (Hypoalbuminemia)
4. Clinical Biochemistry. Merck Veterinary Manual