A diabetic cat that vomits twice, refuses breakfast and sits head-down is not having a bad day. It may be 30 hours from respiratory failure. Three numbers separate a recheck tomorrow from an IV line tonight: blood beta-hydroxybutyrate above 2.55 mmol/L, venous pH below 7.35, bicarbonate below 16 mmol/L. In a 93-cat Pennsylvania study, 39% admitted with diabetic ketoacidosis (DKA) died or were euthanised. A Vienna insulin trial kept survivors hospitalised a median of 5.8 to 7.2 days. This is an inpatient disease.
What counts as DKA: three numbers, not one
Glucose alone misleads: DKA needs hyperglycaemia, ketones and acidosis at once, and the acidosis is the part an owner never sees.
| Test | DKA cutoff | Where it fails |
|---|---|---|
| Blood glucose | >250 mg/dL (13.9 mmol/L) | Euglycaemic DKA can sit at 150–250 mg/dL |
| Venous pH / bicarbonate | pH <7.35 or HCO3 <16 mmol/L | Needs a blood gas; no home meter does this |
| Blood BHB | ≥2.55 mmol/L | 94% sensitive, only 68% specific |
| Urine acetoacetate | 3+ or higher (about 80 mg/dL) | Reads the wrong ketone; lags behind |
Memorise the ketone cutoff. Across 217 paired samples from 138 diabetic cats, a BHB meter reading above 2.55 mmol/L caught 94% of ketoacidaemic cats but flagged 32% that were not acidotic — good for excluding, poor for confirming. In 20 confirmed Vienna cases, admission BHB ran 6.3 to 7.6 mmol/L, about three times the threshold, with pH 7.19 to 7.20.
Normal blood glucose does not rule it out
Cats on the oral gliflozins — bexagliflozin (Bexacat) and velagliflozin (Senvelgo) — can be acidotic with a glucose of 180 mg/dL. They push glucose out through the kidneys, so the meter looks calm while fat breakdown continues. In the velagliflozin field data, euglycaemic DKA accounted for 78% of DKA episodes; overall it hit 5–7% of insulin-naive cats, 18% of cats switched off insulin, and 86% of cases appeared within the first two weeks. If a cat on a gliflozin starts vomiting, stop the tablet and treat it as an emergency whatever the glucose — the glucose-lowering effect can persist for days, and the cat still needs insulin plus dextrose.
The signs that decide the next hour
The classic triad is vomiting, dehydration and acetone breath, but acetone is faint and late — most owners never smell it. Watch these:
- Vomiting twice in 12 hours, especially with refusal of food for more than 24 hours.
- Dehydration of 5% or more: tacky gums, a skin tent that stays up, sunken eyes.
- Dull mentation: the cat stands but stares, or cannot rise without help.
- Fast, deep breathing — the body blowing off acid. A sleeping rate above 30 breaths per minute is abnormal in any cat.
- Low body temperature: under 37.2 °C (99 °F) means poor perfusion, not a cold room.
Urine strips read the wrong ketone
Dipsticks measure acetoacetate and acetone with a nitroprusside reaction. They cannot see beta-hydroxybutyrate, the dominant ketone in DKA, and they under-read badly at high concentrations.
| Dipstick grade | Acetoacetate (mg/dL) | What it means in a diabetic cat |
|---|---|---|
| Negative | 0 | Ketosis unlikely today |
| Trace | 5 | Recheck in 24 hours |
| 1+ | 15 | Mild ketosis; call the vet |
| 2+ | 40 | Same-day appointment |
| 3+ | 80 | Emergency if the cat is off food or vomiting |
| 4+ | 160 | Emergency regardless of how the cat looks |
Context decides. The 2026 AAHA guidelines note that well diabetic cats occasionally have ketonuria, so a 1+ strip in a cat eating normally is a recheck, not a 2 a.m. drive; a 3+ strip in a cat that stopped eating is the opposite.
The first six hours in hospital
Treatment is fluids, electrolytes, insulin and a hunt for the trigger — pancreatitis, urinary infection, dental disease. None of it is quick at home.
Fluid deficit is estimated as percentage dehydration × body weight in kg × 1000 mL, replaced over 6–12 hours (12–24 with heart disease), plus maintenance near 2 mL/kg/hour. Potassium comes first: most DKA cats are total-body depleted even when serum potassium reads normal, and guidelines want 3.0–3.5 mmol/L before the first insulin dose. Vienna admission medians were 2.5 and 3.15 mmol/L. Phosphorus is the cat-specific trap — hypophosphataemia causes haemolysis far more readily than in dogs.
| 50% dextrose added to 1 L of crystalloid | Final concentration |
|---|---|
| 25 mL | 1.25% |
| 50 mL | 2.5% |
| 100 mL | 5% |
| 150 mL | 7.5% |
Dextrose goes in once glucose nears 250 mg/dL, holding it at 150–250 while ketones clear. Insulin starts within 4–6 hours; the protocol and dose belong to the treating vet, not a website.
48 hours or five days: the real timeline
Owners ask "how long". Ketones are the clock, not glucose. In the Vienna trial, BHB fell below 2.55 mmol/L at a median of 30 hours on a constant-rate insulin infusion and 42 hours on a glargine protocol; the range ran 12 to 102 hours. Discharge came at 140 hours (5.8 days) and 174 hours (7.2 days). Eight of the 20 cats needed a feeding tube because anorexia outlasted three days. The 2026 AAHA guidance is explicit that glucose need not be normalised before discharge — the cat must be stable, rehydrated and eating.
What it costs, and where the bill comes from
| Tier | Typical total | What it buys |
|---|---|---|
| Conservative | $1,500–2,500 | Exam, labs, fluids, insulin, 1–2 days |
| Standard | $2,500–4,500 | Serial glucose, electrolytes, 2–4 days |
| ICU / referral | $4,500–8,000 | Blood gases, imaging, 3–5+ days |
US emergency DKA treatment averages about $3,200, ranging from $1,500 to $6,000 and up. Nursing hours and repeat blood work drive the bill, not insulin: routine diabetes care runs $800–2,000 a year, while one ICU night can cost more than a year of insulin.
Who survives, and what shifts the odds
Of 93 cats with DKA, 36 (39%) had a poor outcome — death or euthanasia. Published mortality runs 17% to 50%. DKA cats were younger than uncomplicated diabetics (median 9.4 versus 11.6 years), Siamese were over-represented, and a poor outcome tracked with higher admission creatinine, BUN, total magnesium and bilirubin — kidney injury and liver involvement, not the glucose value. The Vienna trial discharged 17 of 20 cats (85%). Recurrence is real: any infection or missed dose restarts the cycle, so the trigger hunt matters as much as the fluids.
Ten minutes at home before you drive
- Call the emergency hospital and say "diabetic cat, vomiting, ketones" — that phrase moves you up the queue.
- Do not give the next insulin dose at home. Without potassium and fluid support it can drop the cat into shock or hypoglycaemia (under 60 mg/dL is its own emergency).
- Bring the insulin pen, the meter, the food label and a photo of the litter box.
- Offer water in small amounts; withhold food if the cat is vomiting.
- Keep the cat warm on the drive. Hypothermic cats do worse.
This article does not replace a veterinary diagnosis. DKA is confirmed with blood gas and ketones in hospital, and every treatment decision — insulin type, dose, fluid rate, potassium — belongs to a vet who has examined the cat. If you suspect DKA, call an emergency clinic now, not in the morning.
Terms mentioned in this article
Frequently asked
Can a cat have DKA with a normal blood glucose?
Yes. Cats on the SGLT2 inhibitors bexagliflozin or velagliflozin can be acidotic at 150–250 mg/dL, and 78% of DKA episodes in the velagliflozin field data were euglycaemic. Any diabetic cat that vomits or stops eating needs ketones checked, whatever the glucose meter says.
Is a 3+ urine ketone strip always an emergency?
Not by itself. A 3+ strip (about 80 mg/dL acetoacetate) in a cat that is eating, drinking and behaving normally is a same-day recheck; the same strip in a cat that has vomited or refused food for 24 hours is an emergency. The 2026 AAHA guidelines note that well diabetic cats occasionally have ketonuria.
How long will a cat with DKA stay in hospital?
Plan for 3 to 7 days. In a 20-cat trial, blood ketones fell below 2.55 mmol/L at a median of 30 to 42 hours and discharge came at 140 to 174 hours. Cats go home when they are stable, rehydrated and eating — not when glucose is perfect.