Lactate in cats and dogs

What it shows

Cells turn glucose into pyruvate for energy. When there is not enough oxygen, pyruvate is converted into lactate instead, and lactate builds up in the blood. The liver and other tissues normally clear it fast: in healthy animals its half-life is about 20–60 minutes. So lactate reflects what is happening now, and it falls quickly once the cause is corrected.

Vets divide high lactate into two kinds. Type A comes from tissues not getting enough oxygen — poor circulation or too little oxygen-carrying blood. Type B happens without such a lack of oxygen — from illness, medicines, toxins or reduced clearance. A raised lactate does not always mean the blood is acidic, but a large build-up can cause lactic acidosis.

Higher than reference — what it may be a sign of

• Poor oxygen delivery (type A): shock, severe loss of circulating volume from dehydration, acute severe anaemia, loss of blood supply to part of the body.
• Illness without lack of oxygen (type B): sepsis, diabetes (particularly with ketoacidosis), cancer, acute liver failure, which slows lactate clearance.
• Medicines and toxins: some drugs, including glucocorticoids and paracetamol (acetaminophen), and ethylene glycol (antifreeze). In two dogs with ethylene glycol poisoning a falsely high value was also measured.
• Muscle work: exercise raises lactate, but the body clears it quickly.

In a dog with gastric dilatation-volvulus a high lactate before surgery points to a higher chance that the stomach wall is damaged.

Lower than reference

The sources describe no disease that a low lactate points to; a vet looks at high values and how they change. A falling lactate after the vet has started to stabilise the animal is a good sign, because it means oxygen delivery is improving or the cause is being removed.

Look at together with

• Blood gases, bicarbonate and the anion gap — lactate is an acid; its build-up uses up bicarbonate and raises the anion gap.
• Glucose and ketones — when diabetes or ketoacidosis may be the cause.
• Hematocrit — severe anaemia reduces oxygen delivery.
• Blood pressure and other vital signs — lactate is one of the measures vets use to judge circulation and to track change in critically ill animals.

Units and conversion

Lactate is reported in mmol/L; some forms use mg/dL. One mg/dL equals 0.111 mmol/L, so 9 mg/dL is about 1 mmol/L. Portable analyzers differ, so results from two devices are not compared directly. In the app each row keeps the unit printed on the form; the chart converts to one unit.

Reference range

The reference range is on your lab’s form — or on the printout of the clinic’s analyzer. Ranges differ between laboratories. The sample has to be analysed fast, because blood cells keep metabolising in the tube and change the lactate value. In emergency care the trend matters most: lactate is measured again to see whether it comes down, and in dogs a lactate that stays high despite care is associated with a poorer outlook. For gastric dilatation-volvulus, the Merck Veterinary Manual notes that lactate above 6 mmol/L is associated with a higher likelihood of stomach wall necrosis.

Cats and dogs

Sources

1. eClinPath (Cornell University College of Veterinary Medicine) — Specific acid-base disturbances (L-lactic and D-lactic acidosis)
2. eClinPath (Cornell University College of Veterinary Medicine) — Acid-base: laboratory detection
3. Winkler KP. Gastric Dilation and Volvulus in Small Animals. Merck Veterinary Manual
4. Linklater A. Initial Triage and Resuscitation of Small Animal Emergency Patients. Merck Veterinary Manual