Beta-hydroxybutyrate and blood ketones in cats and dogs

Beta-hydroxybutyrate (BHB) is the main ketone body in the blood — a fuel the liver makes from fat when cells cannot use sugar. In a healthy cat or dog it is very low. On a form it matters most in diabetes: a clearly raised BHB tells the vet that ketones are building up, which can turn into diabetic ketoacidosis, a dangerous emergency.

SectionBiochemistry

SampleBlood (serum or plasma with heparin or EDTA) for a laboratory test; a drop of blood for a handheld meter; heparinised plasma for a strip test

Unitsmmol/L

On formsBHB

What it shows

When insulin is missing or the body is starving, fat is broken down and the liver turns the fatty acids into ketone bodies: acetoacetate, BHB and acetone. Ketones are acids. A moderate rise (ketosis) does not always upset the blood’s acid balance, but a large one causes ketoacidosis. In diabetic ketoacidosis BHB is the ketone that rises most.

On a form there may be two lines:

Beta-hydroxybutyrate (BHB) — a number in mmol/L from a laboratory analyser or from a handheld ketone meter, the kind used in clinics.
Blood ketones (dipstick) — a quick qualitative test, usually done by wetting the ketone pad of an ordinary urine strip with plasma instead of urine. This pad reacts mainly to acetoacetate and does not detect BHB at all, so it can underestimate ketones.

Urine ketones (a separate article) are measured by the same pad and have the same blind spot for BHB.

Higher than reference — what it may be a sign of

Diabetic ketosis and ketoacidosis — the main reason to measure BHB in cats and dogs. In ketoacidosis BHB is markedly increased, usually together with an acidic blood picture (high anion gap, low bicarbonate) and ketones in the urine. Infection, pancreatitis or kidney problems can push a diabetic animal into ketosis.
Starvation or a long period without eating — fat is used for energy and ketones rise.
Hard exercise in dogs — a rise from fat burning.
Blood ketone strip positive — acetoacetate was found in plasma. The vet reads it with glucose and the acid–base picture; the strip gives no number.

Lower than reference

In health BHB is very low, and a low value has no clinical meaning of its own. A negative blood ketone strip makes ketoacidosis less likely and is used as a quick “rule-out” test, but because the pad misses BHB, it cannot exclude ketosis completely. In a study of diabetic cats, a urine strip wetted with plasma stayed negative in cats with BHB 0.2–0.9 mmol/L, which shows how much a strip can miss.

Look at together with

Glucose and fructosamine — how high blood sugar is now and over the past weeks.
Urine ketones — the same chemistry in urine; ketones usually appear in urine before they climb in blood.
Bicarbonate and anion gap — show whether ketones have already made the blood acidic.

Units and conversion

BHB is reported in mmol/L, and there is nothing to convert. Handheld meters give a number in the same units, but a meter can read differently from a laboratory analyser, especially at high values, so meter and lab results are compared with care. The blood ketone strip is qualitative: the form says “negative”, “trace” or a grade such as “small” or “moderate”, the same way urine ketones are written. The app stores the strip result as text.

Reference range

The reference range is on your lab’s form. In health BHB is close to zero, and the meaning lies in how high it is in an unwell diabetic animal. In one study, healthy cats had plasma BHB of 0–0.1 mmol/L, and 2.4 mmol/L was proposed as the cut-off for ketoacidosis: all cats with ketoacidosis in the study were above it. A veterinary review cites about 3.8 mmol/L for dogs. These are study cut-offs, not a reference range, and ketoacidosis is diagnosed by the vet from the whole picture, including blood acidity.

Cats and dogs

Cats

Diabetic cats can develop ketosis and ketoacidosis, and BHB has been shown to be a useful test for both in cats. One handheld meter tested in cats was accurate below about 4 mmol/L but read too low above that, and results of one meter cannot be transferred to another.

Dogs

In dogs BHB is measured for the same reason — suspected diabetic ketosis or ketoacidosis. Hard exercise can raise it a little in healthy dogs. Handheld meters are used in clinics as a quick check and studies, mostly in cats, report good agreement with laboratory methods, but the vet decides from the whole picture, not from the meter alone.

In the app

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.

Open the app

Sources

Updated 6 November 2026 · Mihail Ivanov, creator of Pet Tracker Space · Written with Claude and checked against the sources above.

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.