Blood glucose curves for diabetic cats, explained

A blood glucose curve for a cat maps how insulin works over 12 hours. Learn what the nadir and duration mean and why home and CGM monitoring now lead the way.

2026-03-03

Articles · Diabetes

If your veterinarian has mentioned running a “curve” on your diabetic cat, it can sound clinical and intimidating. In reality, a blood glucose curve is just a series of glucose readings taken across the day to show one thing: how your cat’s body responds to insulin from one dose to the next. Understanding what the curve reveals helps you have a far more productive conversation with your vet about whether the current plan is working.

This article is educational. Your veterinarian interprets your cat’s curve and makes all treatment decisions.

What is a blood glucose curve?

A blood glucose curve is a graph built from multiple glucose measurements taken over a dosing interval, usually about 12 hours for cats. Instead of judging treatment from one snapshot, the curve shows the full arc: where blood sugar starts, how low it goes after insulin, and how long the insulin keeps it controlled.

The traditional approach begins at the time of the insulin dose (time zero) and samples glucose roughly every two hours for the next 10 to 12 hours, according to the 2018 AAHA Diabetes Management Guidelines. Connecting those dots produces a curve that tells your veterinarian whether the dose, the timing, and the insulin type are a good match for your individual cat. One reading can mislead; the shape of the whole curve is what carries the information.

What do the nadir and duration actually mean?

The two most important features of a curve are the nadir (the lowest glucose value) and the duration of effect (how long the insulin keeps glucose controlled). Together they tell your vet whether the dose is too high, too low, or about right, and whether the insulin lasts long enough between doses.

The AAHA describes an ideal nadir, the lowest point, of roughly 80 to 150 mg/dL, with many clinicians aiming for a low point near 100 mg/dL. On a textbook 12-hour curve, glucose starts and ends in a moderate range, dips to that nadir several hours after the dose, then rises again before the next injection. If the nadir is too low, the dose may be excessive and risk hypoglycemia. If glucose never comes down meaningfully, the dose or insulin choice may need review. Crucially, duration of action cannot be judged until the nadir is in an acceptable range first, which is why your vet looks at the whole picture rather than any single value.

Why can a curve look strange even when you did everything right?

Curves are influenced by stress, appetite, activity, and the cat’s own counter-regulatory hormones, so an odd-looking curve does not mean you made a mistake. One well-known pattern is rebound hyperglycemia, sometimes called the Somogyi effect, where blood sugar drops low and the body overcorrects by releasing hormones that push glucose back up, producing a confusingly high reading.

It is worth knowing that this rebound pattern appears to be genuinely uncommon in cats on modern long-acting insulin. Research on glargine-treated cats found rebound hyperglycemia occurred in fewer than 1 in 200 daily glucose curves. The bigger and more frequent confounder is stress: a nervous cat at the clinic can show falsely high readings that do not reflect its real day. This is one reason home and sensor-based monitoring have become so valuable.

Why are home and continuous monitoring now preferred?

Because stress at the veterinary clinic can distort a cat’s glucose readings, monitoring at home gives a truer picture of daily life. The 2026 AAHA Diabetes Management Guidelines for Cats move away from in-hospital blood glucose curves and lean toward home data and continuous glucose monitors (CGMs) instead.

A continuous glucose monitor is a small sensor worn on the skin that measures glucose in the fluid just under the skin, automatically, about every 15 minutes for up to 14 days, as the AAHA describes. Rather than a handful of pricks across one stressful clinic day, a CGM produces a smooth, detailed picture across many ordinary days and nights, including the overnight hours a spot check would miss. For families who prefer spot checks, a small ear or paw prick read on a pet glucometer at home still avoids clinic stress and contributes useful data. For the bigger management picture, see our feline diabetes management guide.

How should I read my cat’s curve without overreacting?

The single most useful habit is to read curves as a trend over time, not as a verdict on any one day. A curve is a tool for your veterinarian to fine-tune the plan; it is not a number you should act on by adjusting insulin yourself.

Look at the overall shape with your vet: Did glucose come down after the dose? Did it dip too low? Did it stay controlled until the next dose, or rise early? Pair the curve with what you observed that day, including appetite, water intake, energy, and litter box habits, because context explains a lot of variation. If a curve shows a low nadir or your cat seemed weak, wobbly, or unusually quiet, treat that as a safety flag to discuss promptly rather than a cue to change the dose. Our guide to hypoglycemia warning signs explains what a dangerous low looks like and the general emergency response.

How does a glucose curve guide treatment decisions?

A curve helps your veterinarian decide whether to keep the current dose, adjust it, change the insulin type, or alter timing, always as a clinical judgment, never a do-it-yourself calculation. Multiple curves over weeks reveal whether your cat is trending toward stable control or even toward remission.

Each curve answers specific questions: Is the dose reaching an appropriate nadir without going too low? Is the insulin lasting the full interval? Is glucose control improving compared with previous sessions? Because these decisions hinge on accurate, well-recorded data, keeping organized notes between curves matters as much as the curve itself.

Pawtient AI’s glucose curve sessions let you log a series of timed readings and pair them with that day’s meals, doses, and symptoms, so the pattern is clear when you review it with your veterinarian instead of buried in scattered notes. You can see how it works at /pawtient/features or in the diabetic-cat workflow. If a lab result confuses you, our lab value translator and FAQ can help you frame better questions.

Pawtient AI is an AI assistant and second opinion, never a diagnosis, always consult your veterinarian.

Sources

By Pawtient AI Editorial Team. Educational content reviewed against published veterinary guidelines (IRIS, AAHA, WSAVA, ACVIM, AAFP). Not a substitute for veterinary care.

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