A 12-hour glucose curve is 7 blood readings taken at 0, 2, 4, 6, 8, 10 and 12 hours after the morning insulin, and its job is to show the lowest point, not the average. The target range for most treated cats is 100–300 mg/dL, with the nadir between 100 and 150 mg/dL. Run 1 curve every 3–6 days while the dose is being changed, then 1 every 3–6 months once 2 curves in a row look the same.
The 7 points and what each one tells you
The first reading is taken before the injection and shows whether the previous dose wore off. The 4-hour to 6-hour readings usually catch the nadir. The 12-hour reading shows whether the cat is drifting low overnight, which is the reading most home curves skip and the one that explains a cat that looks fine at 9 am and shaky at 7 pm.
| Time | Expected mg/dL | What it decides |
|---|---|---|
| 0 h (pre-insulin) | 150–300 | If above 300, the previous dose did not last 12 hours |
| 2 h | 150–280 | Onset check; a flat 2 h with a high 0 h means slow absorption |
| 4 h | 110–220 | Early descent; a drop of 150 mg/dL in 4 hours is too fast |
| 6 h | 100–180 | Usual nadir window for most cats |
| 8 h | 110–220 | Confirms the nadir passed and glucose is climbing |
| 10 h | 150–280 | Duration check before the next injection |
| 12 h | 150–300 | Cycle close; below 100 here risks an overnight low |
Sampling at home: 0.3 µL and 5 seconds
Most pet meters need 0.3–1.0 µL, which is less than a grain of rice. Warm the ear for 20–30 seconds with a rice sock or your palm, use a 26–28 gauge lancet on the marginal ear vein, and wipe the first drop away because it carries tissue fluid. Read the second drop. Alternate ears each time so 7 punctures in 12 hours do not turn into 1 sore ear, and log the time to the minute, because a reading at 6 h 40 min is not a 6 h reading.
Strips cost about $1–2 each, so a 7-point curve runs $7–14 in consumables plus the meter. A clinic curve with 7 lab glucose readings usually costs $80–150. Handheld meters read 10–15% lower than a lab analyzer on cat blood, which matters at the bottom of the range: a meter reading of 60 mg/dL may be 68 on a lab, and a meter reading of 250 may be 275.
Why 100–300 and not 80
Below 100 mg/dL the margin for error disappears, and a cat that dips to 60 can seizure within 20 minutes. Above 300 mg/dL for more than 4 hours, glucose spills into urine, the cat drinks more, and the risk of a ketoacidotic crisis climbs. Some vets aim tighter, 80–200 mg/dL, in cats that still make their own insulin and may reach remission, but that target needs a curve every 3–7 days and a vet who answers the phone at night.
The 2 curve shapes
Flat curve. The difference between the highest and lowest reading is under 100 mg/dL, and the 12-hour value sits within 40 mg/dL of the 0-hour value. This usually means the dose is too low, or the insulin is being absorbed slowly. A flat curve with glucose never below 250 for 3 curves in a row is the classic signal to increase, and only your vet should do that.
Deep-nadir curve. Glucose falls below 100 mg/dL around 4–6 hours and then rebounds above 300 by 12 hours, sometimes with a swing of 250 mg/dL or more. The rebound is the body answering a low with adrenaline and glucagon, and the fix is not more insulin. Increasing the dose on this shape drives the nadir lower and the rebound higher, which is how cats end up in hospital.
A third pattern looks like a deep nadir but is really a missed injection or an insulin that was warm for 6 hours. Check the pen temperature and the injection log before you change anything.
How often, and what to record
During a dose change, 1 curve every 3–6 days, and never 2 dose changes without a curve between them. Once 2 consecutive curves stay inside 100–300 mg/dL with a nadir above 100, move to 1 curve every 3–6 months, plus a fructosamine at each visit, and put the yearly titer and bloodwork review on the same day. Record food intake in grams, water in mL, urine clumps per day, and the insulin units actually given; a curve without those 4 numbers cannot be read.
Reference intervals and result days
Normal fasting glucose in a cat is 70–150 mg/dL, and stress alone can push a healthy cat to 200–250 mg/dL in the clinic. Fructosamine reference is roughly 200–350 µmol/L and reflects the previous 2–3 weeks; a value above 400 supports poorly controlled diabetes, and a value under 350 in a cat with high glucose points to stress rather than diabetes. In-house glucose returns in 5 seconds, fructosamine in 1–2 days, and a full curve report the same day.
Between curves, the routine in our guide to home glucose curves applies: 2 readings a day, 1 before the injection and 1 at the suspected nadir, which catch a downward trend 3–5 days before a scheduled curve would. Urine ketone strips, about $10 for 50, are worth keeping for any day the cat vomits or stops eating.
When to see a vet
Call the clinic the same day for a meter reading under 60 mg/dL, 2 readings above 350 mg/dL in 1 day, vomiting more than twice, refusal to eat for 12 hours, weakness or wobbling, or positive urine ketones. Signs of low blood sugar, including trembling, head tilt, and collapse, need a fast response at home and a call to the vet immediately after. Never change a dose on your own; insulin type, units, and timing are set by your vet, and every dose in this article is by veterinary prescription only.
5 steps for a usable curve
- Fast the cat for 2 hours before the first reading, then feed at the normal time.
- Take 7 readings at 0, 2, 4, 6, 8, 10 and 12 hours, timed to the minute.
- Warm the ear 20–30 seconds and wipe the first drop away.
- Write down grams eaten, water drunk, urine clumps, and units given.
- Send the whole sheet to your vet; 1 curve every 3–6 days until 2 match.
Frequently asked
Can I do a curve with 3 readings instead of 7?
Three readings catch a trend but often miss the nadir, which most cats reach between 4 and 6 hours. A 0, 6 and 12 hour check is better than nothing, and it is what many owners manage on a workday, but use a full 7-point curve every 3 to 6 days while the dose is moving, and treat any reading under 100 mg/dL as a reason to call the clinic.
Why does my cat glucose go up right after insulin?
That is usually a rebound, not a failure of the insulin. Glucose falls below 100 mg/dL around 4 to 6 hours, the body releases adrenaline and glucagon, and the 8 or 12 hour reading ends up above 300 mg/dL with a swing of 200 mg/dL or more. The answer is a lower dose or a longer-acting insulin, both set by your vet, never a higher dose.
How do I know the meter is accurate enough?
Compare it once with a lab glucose from the same visit; handheld meters typically read 10% to 15% lower on cat blood. If your meter reads 60 and the lab reads 68, the gap matters, because 60 is already a call-the-vet number. Check strips are in date and the meter is coded to the strip lot before you trust a curve.