Feline diabetes mellitus is one of the most common endocrine disorders of cats, with an estimated prevalence of 1 in 200 to 1 in 400 in the general cat population, rising considerably in older and overweight cats. It is also one of the most manageable chronic conditions in cats — with the right insulin protocol, dietary strategy, and monitoring approach, many diabetic cats achieve excellent quality of life, and a meaningful proportion achieve complete diabetic remission.

This article covers everything an owner or veterinary professional needs to know about managing feline diabetes: understanding the pathophysiology, selecting and administering insulin, monitoring glucose at home, recognising and responding to hypoglycaemia, and working toward remission.

Understanding Feline Diabetes

Feline diabetes mellitus shares more features with human type 2 diabetes than with type 1. The underlying processes include progressive insulin resistance — where body cells become less responsive to insulin — and gradual beta-cell (insulin-producing cell) dysfunction and loss in the pancreatic islets of Langerhans. Risk factors that drive insulin resistance include obesity, physical inactivity, male sex, glucocorticoid administration, and certain concurrent diseases.

Unlike in dogs (where type 1 insulin-dependent diabetes is the norm), a proportion of diabetic cats — particularly those diagnosed early before significant beta-cell loss has occurred and managed intensively — can recover adequate pancreatic function and no longer require insulin. This is diabetic remission, and it is a realistic treatment goal that profoundly influences the choice of insulin and management protocol.

Diabetic Remission in Cats Remission rates of 50–100% have been reported in cats managed with glargine or detemir insulin combined with a low-carbohydrate diet and intensive glucose monitoring. The probability of remission is highest when diabetes is diagnosed and treated promptly, before extensive beta-cell loss. Every week of suboptimal glycaemic control reduces remission probability.

Clinical Signs

The classic clinical signs of feline diabetes reflect the effects of persistent hyperglycaemia and relative insulin deficiency:

• Polyuria and polydipsia (PU/PD): Increased urination and thirst are often the first signs owners notice, resulting from glucose-induced osmotic diuresis.
• Polyphagia with weight loss: Increased appetite despite weight loss reflects the inability of cells to utilise glucose without insulin. Muscle and fat are catabolised for energy.
• Plantigrade stance: A distinctive and diagnostically useful sign unique to cats — weakness of the hind limbs causing the cat to walk on its hocks rather than its toes. This reflects diabetic neuropathy affecting peripheral nerves.
• Lethargy and poor coat condition: Non-specific signs of metabolic dysfunction common to many chronic conditions.
• Diabetic ketoacidosis (DKA): In severe or undiagnosed cases, the breakdown of fat produces ketone bodies, causing acidosis, vomiting, collapse, and a characteristic sweet or ‘pear drop’ odour to the breath. DKA is a medical emergency.

Diagnosis

Diagnosis requires demonstration of persistent hyperglycaemia with concurrent clinical signs. A single elevated blood glucose result is insufficient — cats are physiologically prone to stress hyperglycaemia, which can transiently elevate glucose to diabetic levels in a frightened cat during a veterinary visit.

Fructosamine and glycated haemoglobin (HbA1c equivalent) reflect average glucose over 2 to 3 weeks and 6 to 8 weeks respectively, and are not affected by acute stress. They are the most reliable diagnostic biomarkers to confirm true, sustained hyperglycaemia. Urine glucose (glucosuria) supports the diagnosis and can be used for monitoring but is a relatively insensitive indicator of glycaemic control.

Test	What It Measures	Clinical Use
Blood glucose (spot)	Glucose at moment of testing	Screening; affected by stress — interpret cautiously in clinic
Fructosamine	Average glucose over ~2–3 weeks	Confirms sustained hyperglycaemia; monitors medium-term control
Urine glucose dipstick	Presence of glucose in urine	Home monitoring; cannot distinguish well vs. poorly controlled
Continuous glucose monitor (CGM)	Glucose every 5–15 minutes over days	Gold standard for glucose curve; stress-free home monitoring
Serial blood glucose curve	8–10 glucose readings over 12–24h	In-clinic assessment of insulin effect; stressful for some cats

Insulin Selection

The choice of insulin is one of the most consequential decisions in feline diabetes management. Cats have a uniquely long duration of insulin action compared to dogs and humans, and their metabolism differs significantly from the human physiology that most insulin formulations were designed for.

Glargine (Lantus) — First-Line Recommended

Insulin glargine is a long-acting peakless (flat-profile) insulin analogue that provides smooth, sustained basal insulin coverage. It is the most studied insulin in cats and is associated with the highest remission rates — approximately 50 to 100% in appropriately selected cats when combined with a low-carbohydrate diet and intensive monitoring. Glargine is administered subcutaneously every 12 hours (q12h) in cats.

Detemir (Levemir) — Alternative Long-Acting

Insulin detemir is another long-acting analogue with similar pharmacological properties to glargine. It tends to be more potent on a unit-per-unit basis, requiring lower doses. Remission rates comparable to glargine have been reported. An advantage in some cats is a longer effective duration of action, potentially improving overnight glycaemic control.

Protamine Zinc Insulin (PZI) — Species-Appropriate

PZI (ProZinc) is the only insulin specifically licensed for use in cats in many countries. It provides intermediate to long duration of action in cats and is a reliable first-line choice, particularly when owner monitoring intensity is limited. Remission rates with PZI are somewhat lower than with glargine in comparative studies.

Insulins to Avoid in Cats

NPH (neutral protamine Hagedorn) insulin, despite being widely used in human and canine diabetes management, has a shorter, peakier action profile in cats and is associated with hypoglycaemic episodes and poor glycaemic control. It should be avoided in cats except in specific clinical circumstances. Premixed human insulins (e.g., 70/30 formulations) are similarly inappropriate for routine feline diabetes management.

Starting Insulin: Dosing Principles

Initial insulin dosing in cats is conservative to minimise hypoglycaemia risk. Standard starting doses:

• Glargine or detemir: 0.25 to 0.5 IU/kg q12h. Start at the lower end for cats with blood glucose below 20 mmol/L (360 mg/dL) or cats with low body weight.
• PZI (ProZinc): 0.2 to 0.4 IU/kg q12h. Similar conservative starting principle.

Dose adjustments are made based on glucose curve results, typically in increments of 0.5 to 1 IU. Overly aggressive dose increases significantly increase hypoglycaemia risk and may paradoxically worsen glycaemic control through the Somogyi effect (rebound hyperglycaemia following hypoglycaemia).

Insulin Administration Technique

Correct administration technique is essential for consistent insulin delivery and glycaemic control. Key principles:

• Injection site: Subcutaneous injection into the scruff (back of the neck) or lateral thorax. Rotate injection sites to prevent lipodystrophy.
• Syringe or pen: Use U-100 syringes for U-100 insulins (glargine, detemir). Use specific U-40 syringes for U-40 formulations. Mismatched syringes cause significant dosing errors.
• Storage: Glargine and detemir should be refrigerated (2–8°C) but never frozen. Once opened, glargine at room temperature has a shelf life of approximately 28 days; refrigerated up to 3 months.
• Timing relative to meals: Administer insulin with or immediately after a meal to ensure adequate food intake has occurred. Never administer insulin to a cat that has not eaten — this risks hypoglycaemia.
• Injection technique: Tent the skin gently, insert the needle at a shallow angle (approximately 45 degrees), inject slowly, and withdraw without rubbing the site. Do not bubble or shake insulin vials — roll gently if mixing is needed.

Critical Safety Rule Always ensure your cat has eaten before administering insulin. If your cat refuses to eat, contact your veterinarian before giving the injection. Administering insulin to a fasted cat risks severe hypoglycaemia.

Home Glucose Monitoring

Home glucose monitoring has transformed feline diabetes management. Measuring glucose in the stress-free home environment produces far more clinically useful information than in-clinic curves and enables timely dose adjustment.

Continuous Glucose Monitors (CGMs)

The FreeStyle Libre 2 sensor (Abbott) and similar CGMs can be applied to the scruff of a cat’s neck and continuously measure interstitial glucose every 15 minutes for up to 14 days. This provides an unprecedented view of glycaemic patterns across multiple days and nights, identifying nocturnal hypoglycaemia, the Somogyi effect, and the duration of insulin action. Several veterinary studies have validated CGM use in cats and it is now considered the gold standard for ambulatory glucose monitoring in feline diabetes.

Flash or Spot Blood Glucose

Ear pinna blood glucose measurement using a portable human glucometer is an established home monitoring method. The marginal ear vein is lanced with a lancet or small needle, and a drop of blood is applied to the glucometer strip. Most owners can learn this technique with adequate instruction and practice. Results should be recorded and shared with the veterinary team. Note that some glucometers have better feline validation than others — the AlphaTrak 2 (species-specific calibration for cats and dogs) is widely used and validated.

Hypoglycaemia: Recognition and Response

Hypoglycaemia — blood glucose below 3.0 to 3.5 mmol/L (54–63 mg/dL) — is the most immediately dangerous complication of insulin therapy. Mild hypoglycaemia may resolve spontaneously, but severe hypoglycaemia can cause seizures, coma, and death if not treated promptly.

Signs of Hypoglycaemia

• Weakness, wobbliness, or ataxia
• Disorientation or unusual behaviour
• Muscle tremors or twitching
• Seizures or convulsions
• Collapse or unconsciousness

Emergency Response

• Conscious cat: Apply corn syrup, honey, or glucose gel to the gums and mucous membranes. Do NOT attempt to syringe liquids into the mouth of a semiconscious or convulsing cat due to aspiration risk.
• Unconscious cat: Rub glucose solution on the gums and seek immediate veterinary care. IV dextrose may be required.
• After recovery: Do not administer the next insulin dose. Feed a small meal. Contact your veterinarian to discuss dose reduction before restarting insulin.

Dietary Management

Diet is the second pillar of feline diabetes management alongside insulin. Cats are obligate carnivores with a metabolic adaptation to high-protein, high-fat, low-carbohydrate diets. High dietary carbohydrate intake worsens postprandial hyperglycaemia, increases insulin demand, and reduces the probability of remission.

A low-carbohydrate diet — ideally below 10% metabolisable energy from carbohydrate — is strongly recommended for all diabetic cats. Wet (canned) food is generally preferable to dry kibble, as kibble formulations are typically higher in carbohydrate content and lower in protein. Several prescription diabetic diets are available (Hill’s m/d, Purina DM, Royal Canin Diabetic) but many over-the-counter high-protein wet foods are also appropriate if carbohydrate content is verified.

Key Takeaways

• Feline diabetes resembles human type 2 diabetes; remission is achievable in a significant proportion of cats with early, intensive management
• Glargine or detemir insulin q12h combined with a low-carbohydrate diet offers the highest remission probability
• Never administer insulin to a cat that has not eaten
• Continuous glucose monitors (CGMs) provide the most comprehensive picture of glycaemic control and are now feasible for home use in cats
• Hypoglycaemia requires immediate treatment with glucose — always keep corn syrup or glucose gel at home
• The goal is not just glucose control, but remission — regular reassessment of whether insulin is still needed is part of good diabetic management

References

1. Roomp K, Rand J (2009). Intensive blood glucose control is safe and effective in diabetic cats using home monitoring and treatment with glargine. J Feline Med Surg 11(8):668–82.

2. Niessen SJ et al. (2010). Feline diabetes mellitus: update on diagnosis and management. J Feline Med Surg 12(5):391–400.

3. Zini E et al. (2010). Predictors of clinical remission in cats with diabetes mellitus. J Vet Intern Med 24(6):1314–21.

4. Gostelow R et al. (2014). Systematic review of feline diabetic remission: separating fact from opinion. Vet J 202(2):208–18.

5. Hafner M et al. (2021). Evaluation of a flash glucose monitoring system in cats with diabetes mellitus. J Vet Intern Med 35(3):1314–22.

6. Bennett N et al. (2006). Comparison of a low carbohydrate-low fiber diet and a moderate carbohydrate-high fiber diet in the management of feline diabetes mellitus. J Feline Med Surg 8(2):73–84.