When to see a vet urgently
Contact a vet promptly if a glucose metabolism disorder is accompanied by any of the following:
- Your cat vomits, does not eat and becomes very subdued.
- Breathing becomes abnormal or your cat seems dehydrated and very weak.
- A cat receiving insulin develops trembling, staggering or unusual behaviour.
- Your cat has seizures, collapses or loses consciousness.
You can find a vet near you. Weakness during insulin treatment can also be caused by blood glucose being too low, so do not give extra insulin yourself based on symptoms.
Overview
Insulin moves glucose from the blood into cells. In insulin resistance, this mechanism is disrupted, forcing the pancreas to release more insulin. Over time, pancreatic capacity becomes exhausted and diabetes develops. In cats, the condition is strongly associated with excess weight and little exercise.
Initially, increased insulin secretion may keep blood glucose normal, so insulin resistance does not always mean diabetes is already present. Disease development depends on both tissue insulin sensitivity and the function of the pancreas's insulin-producing beta cells. Not every at-risk cat develops symptomatic diabetes.
Persistently high glucose can, in turn, damage beta cell function. This is called glucose toxicity. High blood glucose can therefore maintain a worsening cycle. In some treated diabetic cats, cell function can recover enough to reduce medication needs or achieve remission, but this outcome is not possible for every cat.
Causes
The main causes of insulin resistance in cats include:
- obesity, as excess fat tissue reduces cells' sensitivity to insulin
- little exercise
- chronic stress and high cortisol levels
- hormonal disorders, such as acromegaly and hypercortisolism
- long-term glucocorticoid or progestogen treatment
- type 2 diabetes, both as a cause and a factor contributing to progression
Inflammatory or infectious disease can also make glucose control more difficult. Oral disease, pancreatitis, chronic intestinal disease or a urinary tract infection, for example, can increase insulin requirements. Investigation of a poor treatment response is therefore not limited to diet or the insulin preparation.
Ordinary stress during a veterinary visit can temporarily raise a cat's blood glucose. A single high result therefore neither confirms chronic insulin resistance nor establishes a hormonal disease producing excessive cortisol. Assessment requires symptoms, the overall pattern of measurements and targeted additional tests where necessary.
Risk factors
Insulin resistance is more common in cats that:
- are overweight or obese
- are neutered
- are over 7 years old
- have hormonal diseases, such as acromegaly or hypercortisolism
- are inactive
The risk list does not mean age or neutering alone establishes insulin resistance. The combined effects of weight, muscle condition, activity, medication and disease are assessed individually. Monitoring a symptom-free cat at risk is also different from investigating an already diabetic cat with poor control.
Symptoms
Insulin resistance may initially cause no symptoms, but its signs are associated with disturbed glucose metabolism:
- increased thirst and urination
- obesity or sudden weight loss
- a persistently increased appetite
- lethargy and reduced activity
- difficulty controlling glucose in diabetic cats, with a poor response to insulin treatment
Marked thirst, large urine volumes and weight loss despite a good appetite particularly suggest established diabetes. Obesity alone does not cause the same symptoms in every cat. Monitor drinking, urine amounts in the litter tray and movement as well as weight, and tell your vet about changes.
With excess growth hormone secretion, or hypersomatotropism, a cat may need a lot of insulin, while typical enlargement of the face or paws may not yet be noticeable. Acromegaly refers to tissue overgrowth changes associated with hormone excess. A hormonal cause is therefore not ruled out simply because appearance is normal.
Complications and consequences
Uncorrected insulin resistance leads to:
- development or progression of diabetes
- liver dysfunction, including fatty liver disease
- pancreatitis
- a shorter lifespan
These consequences are not inevitable in every cat, and not every disease listed is caused directly by insulin resistance. Pancreatitis, for example, may itself be an underlying disease making glucose control difficult. Investigations therefore distinguish possible causes, concurrent diseases and consequences of diabetes.
Poorly controlled diabetes can lead to ketoacidosis, in which ketones accumulate and acidity increases in the body. This is different from a symptom-free risk of insulin resistance. A diabetic cat that is vomiting, not eating and subdued needs prompt assessment for ketones and other diseases too.
Diagnosis at the vet
Insulin sensitivity is assessed using:
- blood tests for glucose and fructosamine
- blood glucose monitoring during diabetes treatment
- blood biochemistry, including lipids and liver enzymes
- hormonal tests, such as IGF-1 for acromegaly and cortisol for hyperadrenocorticism
Glucose and fructosamine describe glucose control rather than directly measuring every tissue's sensitivity to insulin. Fructosamine provides information about glucose over a longer period, while a single glucose value reflects the time of measurement. Results are considered alongside clinical signs and other observations. Changes in liver enzymes or blood fats do not confirm insulin resistance on their own either.
A continuous glucose sensor can help reveal variation throughout the day and possible low periods. Measurements are not interpreted in isolation from the cat's condition: a low sensor reading may need confirmation with a blood sample. Longer-term monitoring aims to distinguish persistently poor control, a temporary rise and hypoglycaemia, or low blood glucose, caused by excessive treatment.
In a diabetic cat that is difficult to regulate, insulin storage, handling, injection technique and the suitability of the delivery device are also checked first. You may be asked to demonstrate administration at the clinic. An injection passing through the coat or uncertain administration is not the same as the body resisting insulin. Do not give a replacement injection yourself if unsure.
Excess growth hormone secretion is investigated with IGF-1 measurement and pituitary imaging where necessary. IGF-1 is a growth factor produced in response to growth hormone. Its level may be lower early in diabetes because of insulin deficiency, so sampling time and any repeat testing are planned separately. One early result does not always resolve the suspicion.
Other hormone tests, urine culture, abdominal ultrasound or pancreatic investigations are used according to findings. Not every cat needs every test to the same extent. The aim is to identify a cause affecting treatment response and distinguish it from an administration or measurement problem.
Treatment and changes in insulin requirements
Treatment addresses both any diabetes and factors maintaining insulin resistance. Treating an underlying disease and reducing excess weight can improve insulin sensitivity. If a current medicine promotes resistance, your vet assesses its need and possible alternatives. Do not stop corticosteroid medication yourself, for example.
Insulin requirements can also change during treatment. As inflammation resolves or insulin sensitivity improves, the previous amount of medicine may lower blood glucose too far. Repeated increases based solely on a high reading can therefore be dangerous. Changes follow the clinic's plan and sufficient monitoring information.
If a growth hormone-producing pituitary disease is identified as the cause of insulin resistance, treatment options are assessed separately. Treating the hormonal disease can also alter diabetes management. Ordinary weight control alone does not replace investigation of this cause.
Diabetes medication is not started “just in case” in a symptom-free at-risk cat solely because of excess weight or a single raised glucose value. The initial plan in this situation includes lifestyle assessment, management of any diseases and agreed monitoring. No drug treatment has been shown to reliably prevent diabetes in this group.
Feeding and monitoring at home
Weight management for an overweight cat is planned to maintain adequate eating and nutrient intake. Diabetic cats often receive a low-carbohydrate diet, but the choice also takes account of other diseases and food the cat accepts. A dietary change can affect medication needs, so tell the clinic about it.
Record medicines given, meals, any vomiting, changes in drinking and weight trends. A shared recording method helps the family avoid missed or accidentally duplicated injections. Keep the insulin and delivery device clearly identifiable, and resolve uncertainties before giving medication.
Monitoring success is also assessed from your cat's condition. Reduced thirst, stable weight and normal activity are useful observations, but do not justify stopping medicine on their own. A cat that has achieved remission still needs follow-up because glucose control can deteriorate again later.
Prevention
The risk of insulin resistance can be reduced through:
- maintaining a normal weight
- regular exercise through play and movement
- a balanced, low-carbohydrate diet
- monitoring chronic diseases
- regular blood tests in older cats
No single approach is known to prevent diabetes reliably. However, normal weight, exercise and disease management target modifiable risk factors. Blood and urine testing needs are agreed individually. Monitoring an at-risk cat pays particular attention to new thirst, increased urination and weight changes.
What it means for owners
Insulin resistance in cats is an important precursor to diabetes and a risk factor for complications. Remember that obesity is the greatest threat to a cat's health. Managing diet, losing excess weight and arranging regular veterinary checks help maintain insulin sensitivity and prevent diabetes developing.
Note: this material provides general information and does not replace veterinary advice. Contact a vet immediately if symptoms appear.
Frequently asked questions
Is insulin resistance the same as diabetes?
No. Increased insulin secretion may initially keep glucose normal. Diabetes develops when insulin action and secretion are no longer sufficient to maintain normal control.
Does one high blood glucose result prove insulin resistance?
No. Stress can temporarily raise a cat's glucose. Your vet assesses the result alongside symptoms, other measurements and any necessary investigations.
Can I increase the insulin dose myself?
Do not change it without an agreed treatment plan. A change in underlying disease or insulin sensitivity can make even the previous amount too much, and low blood glucose can be life-threatening.
Can an injection problem cause a poor treatment response?
Yes. Storage, handling, equipment and injection technique are checked before a poor response is interpreted as true insulin resistance. Demonstrate your technique at the clinic where necessary.
This article is for general information only and is not a guide to treatment. If you notice the first signs of illness, contact your vet.
Paw4care editorial team
Sources
- Overview of Diabetes Mellitus in Cats, American Animal Hospital Association, accessed 2026-11-03.
- Recognising and Managing Cats at Risk for DM, American Animal Hospital Association, accessed 2026-11-03.
- Insulin Treatment and Monitoring, American Animal Hospital Association, accessed 2026-11-03.
- Feline Diabetes, Cornell Feline Health Centre, accessed 2026-11-03.
- Growth Hormone and IGF-1 in Cats, Michigan State University Veterinary Diagnostic Laboratory, accessed 2026-11-03.
- Diabetes Mellitus Insulin Treatment in Cats, VCA Animal Hospitals, accessed 2026-11-03.
- Troubleshooting in Diabetic Cats, American Animal Hospital Association, accessed 2026-11-03.