HDL and LDL cholesterol in cats and dogs
HDL and LDL are two kinds of particles that carry cholesterol in the blood. In people their balance is used to judge heart risk, but dogs and cats carry most of their cholesterol in HDL, and the human rules do not carry over. On an animal’s form these fractions are an extra result; a vet reads them next to total cholesterol and triglycerides.
What it shows
Fats do not dissolve in blood, so cholesterol travels inside particles called lipoproteins. Two of them carry most of it: LDL (low-density lipoprotein) takes cholesterol out to the tissues, and HDL (high-density lipoprotein) brings it back from the tissues to the liver. When total cholesterol is high, it is usually because these cholesterol-rich particles have increased.
Here dogs and cats differ from people. In healthy dogs and cats most of the cholesterol in the blood sits in HDL, not in LDL, and they lack the enzyme that in people moves cholesterol from HDL over to LDL. Healthy dogs also have a large HDL particle (HDL1) that is not typically found in healthy humans. So HDL and LDL on an animal’s form are not the human “good” and “bad” cholesterol, and the human heart-risk logic does not carry over.
Detailed lipoprotein profiles in animals come from specialised methods (ultracentrifugation, electrophoresis) used mainly in research. Some analysers can report HDL in dog and cat serum, but what a given HDL or LDL value means for a pet’s health has been studied only in small groups so far.
Higher than reference — what it may be a sign of
- The same reasons that raise total cholesterol. In dogs, without high triglycerides: an underactive thyroid (hypothyroidism), protein loss through the kidneys (nephrotic syndrome), blocked bile flow (cholestasis). High cholesterol is found in about 80% of hypothyroid dogs.
- Together with high triglycerides: diabetes, overactive adrenal glands (hyperadrenocorticism), pancreatitis, corticosteroid medicines.
- Inherited lipid disorders in some breeds — see the dog section below.
- A sample taken soon after a meal — fat from food can affect blood lipids for up to about 12 hours.
Lower than reference
Low total cholesterol is seen with protein-losing gut disease in dogs, with cancer in dogs and cats, and with malabsorption, chronic liver disease, inflammation and Addison’s disease (hypoadrenocorticism). In one small pilot study (13 dogs, 3 cats) low HDL was found in dogs with Cushing’s disease or hypothyroidism, and the authors proposed a total cholesterol/HDL ratio as a marker of lipid-related disease. This is an early idea from a small group, not an established rule.
Look at together with
- Total cholesterol and triglycerides — the standard lipid numbers; a vet looks at them first.
- Thyroid tests (total T4, TSH) — hypothyroidism is a classic cause of high cholesterol in dogs.
- Albumin and urine protein : creatinine — protein loss through the kidneys raises cholesterol.
- Glucose, ALP, bilirubin — for diabetes, adrenal disease and cholestasis.
- Milky (lipaemic) serum — this comes from triglyceride-rich particles; high HDL or LDL alone does not make serum look milky.
Units and conversion
HDL and LDL cholesterol are reported in mmol/L or mg/dL, the same as total cholesterol. One mg/dL equals 0.02586 mmol/L, so 100 mg/dL is about 2.59 mmol/L, and 1 mmol/L is about 38.7 mg/dL. In the app each row keeps the unit printed on the form; the chart converts to one unit so forms from different labs line up.
Reference range
The reference range is on your lab’s form. For lipoprotein fractions it depends strongly on the method. The pilot study above, for example, used a working HDL interval of 60–140 mg/dL for both dogs and cats on one clinic analyser — the range of one study and one device, not a general target. Human LDL and HDL targets do not apply to dogs or cats.
Lipids are best measured in a fasting sample: eating raises blood fats for several hours, and a sample taken after a 12-hour fast reduces post-meal lipaemia.
Cats and dogs
As in dogs, most of a cat’s cholesterol is carried in HDL. In cats high cholesterol is usually linked to cholestasis. Cats with primary hyperchylomicronaemia lack activity of the enzyme that clears fat particles (lipoprotein lipase), and their triglycerides are very high. In the pilot study the highest cholesterol/HDL ratio was in a single diabetic cat — one case, too few to draw conclusions.
Dogs carry most of their cholesterol in HDL; very high cholesterol (above about 750 mg/dL) has been linked to a risk of atherosclerosis in hypothyroid dogs. Lipid problems become more common with age in predisposed breeds such as miniature schnauzers and Yorkshire terriers; high cholesterol without high triglycerides has been described in Shetland sheepdogs, rough collies and Briards.
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
- eClinPath (Cornell University College of Veterinary Medicine). Lipid overview — chemistry / energy metabolism.
- eClinPath (Cornell University College of Veterinary Medicine). Cholesterol — chemistry / energy metabolism.
- Xenoulis PG, Cammarata PJ, Walzem RL, et al. Novel lipoprotein density profiling in healthy dogs of various breeds, healthy miniature schnauzers, and miniature schnauzers with hyperlipidemia. BMC Veterinary Research, 2013; 9:47.
- A pilot study of the total cholesterol/high-density lipoprotein ratio as a prognostic indicator of hyperlipidemia-related diseases in dogs and cats (open access, PMC).
- Weeth LP, Morgan SK. Nutritional Management of Hyperlipidemia. Today’s Veterinary Practice, March/April 2022.
- Heseltine J. Hypothyroidism in Animals. Merck Veterinary Manual, professional version, last updated May 2025.
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.