CONDITION

Diabetes Mellitus in Cats

A metabolic condition involving impaired blood sugar regulation that may be influenced by weight, diet, and other health factors.

Why this matters now

Diabetes mellitus in cats occurs most commonly in middle-aged to older cats, with the majority of cases diagnosed between eight and thirteen years of age. Male cats are affected approximately twice as frequently as females, and certain breeds — particularly Burmese cats in some populations — show increased predisposition. The condition has become increasingly prevalent in domestic cat populations over recent decades, a trend that appears to parallel rising rates of obesity and indoor sedentary lifestyles. The predominant form of diabetes in cats closely resembles Type 2 diabetes mellitus in humans, characterised by a combination of insulin resistance and progressive beta cell dysfunction, distinguishing it from the predominantly Type 1 (immune-mediated) diabetes that occurs more commonly in dogs. Obesity is the single most significant modifiable risk factor, with overweight cats being approximately four times more likely to develop diabetes than cats at a healthy body weight. Other recognised risk factors include physical inactivity, increasing age, male sex, and the use of certain medications — particularly corticosteroids and progestogens — that can induce insulin resistance.

The development of feline diabetes mellitus typically follows a progressive trajectory from initial insulin resistance through compensated hyperglycaemia to overt clinical disease. In the early stages, the pancreatic beta cells compensate for insulin resistance by increasing insulin production, maintaining blood glucose within or near the normal range. As the beta cells become increasingly strained and glucose toxicity begins to impair their function, blood glucose levels rise above the renal threshold, producing glucosuria (glucose in the urine), which drives the characteristic osmotic diuresis and compensatory polydipsia. A unique and clinically significant feature of feline diabetes is the potential for diabetic remission — approximately 25-50% of cats may achieve a state where exogenous insulin is no longer required if the diabetes is diagnosed and managed promptly, the precipitating factors (particularly obesity and glucose toxicity) are addressed, and sufficient functional beta cell mass is preserved. The window for achieving remission may narrow with time, as prolonged hyperglycaemia causes progressive beta cell loss through glucose toxicity and amyloid deposition, eventually making the insulin deficit permanent.

Signals & patterns

Early signals

Increased water intake

Polydipsia — noticeably increased water consumption — is one of the hallmark early signs of diabetes mellitus in cats. Owners may observe the water bowl emptying more quickly than usual, the cat drinking from unusual sources (taps, sinks, plant pots), or spending more time at the water bowl. The increased thirst is a compensatory response to the excessive water loss through the kidneys as glucose spills into the urine (glucosuria) and draws water with it through osmotic diuresis. In multi-cat households, the change may be harder to attribute to a specific cat unless individual drinking habits are monitored.

Increased urination

Polyuria — producing larger volumes of urine more frequently — accompanies the increased water intake and results from the osmotic diuretic effect of glucose in the urine. Owners may notice the litter tray becoming heavier or needing changing more frequently, larger clumps in clumping litter, or occasionally urination outside the litter tray due to increased urgency or volume. Some cats may develop urinary accidents in previously reliable litter tray users, which can be mistakenly attributed to behavioural issues rather than a metabolic condition. The urine is typically dilute and pale.

Increased appetite with weight loss

The paradox of eating more while losing weight is a characteristic feature of diabetes mellitus that can be particularly confusing for owners. Despite increased or maintained food intake (polyphagia), the cat loses weight because insulin deficiency prevents glucose from entering cells effectively, forcing the body to break down fat and muscle for energy. The increased appetite is driven by the cells' inability to access the circulating glucose, creating a state of perceived starvation at the cellular level despite abundant glucose in the bloodstream. In some cats, the weight loss may be substantial before it is noticed, particularly in long-haired breeds where body condition changes may be masked.

Reduced activity or lethargy

Cats with developing diabetes may show a gradual decline in activity levels, spending more time sleeping, showing less interest in play, or appearing generally less energetic. This reflects the metabolic inefficiency of the diabetic state — despite high blood glucose levels, the cells cannot utilise this glucose effectively for energy production, leading to a functional energy deficit. The lethargy may develop gradually and can be easily attributed to ageing, weight gain, or seasonal variation rather than recognised as a potential sign of metabolic disease.

Coat condition changes

A subtle but sometimes noticeable early change in some diabetic cats is a deterioration in coat quality — the fur may become dry, dull, flaky, or unkempt. This can result from a combination of reduced grooming behaviour (due to lethargy or general malaise), altered skin metabolism related to insulin deficiency, and the catabolic effects of poorly regulated diabetes on overall body condition. In long-haired cats, matting may develop in areas that were previously well-maintained, reflecting reduced grooming effort.

Later signals

Plantigrade stance (walking on hocks)

Diabetic neuropathy — damage to peripheral nerves caused by chronic hyperglycaemia — may produce a characteristic plantigrade stance in the hind limbs, where the cat walks with its hocks (ankle joints) touching or nearly touching the ground rather than walking on its toes in the normal digitigrade fashion. This occurs because sustained high blood glucose levels damage the peripheral nerves through a combination of direct glucose toxicity, sorbitol accumulation within nerve fibres (via the polyol pathway), and microvascular changes affecting the blood supply to nerves. The neuropathy typically affects the hind limbs first and may be partially or fully reversible with effective glycaemic control, though recovery can take weeks to months.

Marked muscle wasting

Progressive loss of muscle mass becomes increasingly apparent as the diabetic state persists, with the spine, hip bones, and shoulder blades becoming more prominent as the overlying musculature diminishes. This muscle catabolism results from insulin deficiency preventing cells from taking up glucose and amino acids efficiently, forcing the body to break down its own protein stores for gluconeogenesis and energy production. The combination of muscle wasting with potential concurrent fat loss creates an increasingly gaunt appearance that contrasts with the cat's previous body condition.

Diabetic ketoacidosis signs

If diabetes remains unmanaged or becomes decompensated, the cat may develop diabetic ketoacidosis (DKA) — a serious metabolic crisis characterised by the accumulation of ketone bodies in the blood. Signs of DKA include vomiting, loss of appetite, progressive lethargy and weakness, dehydration, and a distinctive sweet or acetone-like odour on the breath. DKA represents a medical situation where the body's fat-burning emergency response has become self-destructive, producing acidic ketone bodies faster than they can be metabolised or excreted. The transition from uncomplicated diabetes to DKA may be triggered by concurrent illness, infection, or other physiological stressors.

Hepatomegaly and liver changes

Chronic diabetes may lead to hepatic lipidosis (fatty liver disease) or glycogen accumulation within the liver, resulting in liver enlargement that may be palpable on abdominal examination. Cats are particularly susceptible to hepatic lipidosis during periods of reduced food intake, and the metabolic derangements of poorly controlled diabetes can precipitate or exacerbate this condition. Elevated liver enzymes on blood work may reflect these hepatic changes, and in some cases the liver disease becomes a significant concurrent condition that complicates the management of the diabetes itself.

Click to read about the biological mechanisms

How this is usually investigated

Diagnosing diabetes mellitus in cats involves confirming persistent hyperglycaemia while accounting for the well-recognised phenomenon of stress hyperglycaemia in this species. The investigation typically combines blood glucose measurement, fructosamine testing, urinalysis, and assessment for concurrent conditions that may have precipitated or complicated the diabetes.

Blood glucose measurement

Purpose: Measurement of blood glucose concentration is the fundamental starting point for diabetes diagnosis. Persistent hyperglycaemia (elevated blood glucose) is the defining biochemical feature of diabetes mellitus. In cats, a random blood glucose above approximately 14-20 mmol/L (250-360 mg/dL) in conjunction with compatible clinical signs is strongly suggestive of diabetes. Blood glucose can be measured in-house using portable glucometers or through laboratory biochemistry panels.
Considerations: Cats are well known for developing significant stress hyperglycaemia — blood glucose elevations caused by the physiological stress response to veterinary visits, handling, and blood collection. Stress hyperglycaemia can raise blood glucose to levels that overlap with diabetic values (sometimes exceeding 15-20 mmol/L), creating a genuine diagnostic challenge. A single elevated blood glucose reading in an anxious cat does not confirm diabetes, and additional testing is typically needed to distinguish true diabetes from stress-related elevations. Home blood glucose monitoring using ear-prick sampling in a calm environment may provide more representative values in some cases.

Fructosamine measurement

Purpose: Fructosamine is a glycated serum protein that reflects the average blood glucose concentration over the preceding one to three weeks. Because fructosamine levels are not affected by acute stress, they provide a valuable means of distinguishing persistent hyperglycaemia (diabetes) from transient stress hyperglycaemia. An elevated fructosamine level in combination with compatible clinical signs and blood glucose elevation confirms that the hyperglycaemia has been sustained rather than momentary, substantially strengthening the diagnosis of diabetes mellitus.
Considerations: Fructosamine levels can be affected by conditions other than diabetes, including hypoproteinaemia (low protein levels, which can falsely lower fructosamine), hyperthyroidism (which may reduce fructosamine through altered protein turnover), and hyperlipidaemia. The test reflects average glucose over weeks, so it cannot detect recent onset diabetes where the hyperglycaemia has been present for only days. In the context of monitoring established diabetes, fructosamine provides a useful measure of overall glycaemic control but does not capture the day-to-day fluctuations that blood glucose curves reveal.

Urinalysis

Purpose: Urinalysis in suspected diabetic cats typically reveals glucosuria (glucose in the urine), which confirms that blood glucose has exceeded the renal threshold. The presence of ketones in the urine (ketonuria) indicates that the body is breaking down fat for energy due to inability to utilise glucose, which may signal developing or established diabetic ketoacidosis. Urinalysis also provides information about urine concentration (specific gravity), protein levels, and may reveal evidence of concurrent urinary tract infection, which is common in diabetic cats due to the glucose-rich urine providing a favourable environment for bacterial growth.
Considerations: Glucosuria confirms that blood glucose has exceeded the renal threshold at some point but does not distinguish between diabetic glucosuria and stress-induced transient glucosuria in extremely stressed cats. Urine culture is often recommended in newly diagnosed diabetic cats, as urinary tract infections may be subclinical (producing no obvious signs) yet can significantly interfere with glycaemic control. The timing of urine collection relative to food intake and insulin administration affects the interpretation of glucose and ketone levels in cats already receiving treatment.

Assessment for concurrent conditions

Purpose: Comprehensive blood work (haematology, biochemistry, thyroid hormone measurement) is important at the time of diabetes diagnosis to identify conditions that may have precipitated the diabetes, that may complicate management, or that may require concurrent treatment. Hyperthyroidism, chronic kidney disease, pancreatitis, and acromegaly are among the conditions that can coexist with or contribute to feline diabetes. Hyperthyroidism in particular can both mask diabetes (by improving glucose tolerance through increased metabolic rate) and coexist with it, requiring careful consideration of how treating one condition may affect the other.
Considerations: Some concurrent conditions may only become apparent after diabetes management has been initiated — for example, previously compensated kidney disease may become clinically evident once the osmotic diuresis of uncontrolled diabetes is resolved. Pancreatitis is common in diabetic cats and can be challenging to diagnose definitively with standard tests, potentially requiring serial monitoring and specific pancreatic markers. Acromegaly (growth hormone excess) and hyperadrenocorticism (Cushing's disease), while less common, should be considered in cats with diabetes that proves unusually difficult to control.

Blood glucose curves

Purpose: A blood glucose curve involves serial blood glucose measurements taken every one to two hours over an eight to twelve-hour period, providing a profile of how blood glucose rises and falls in response to insulin, food, and activity throughout the day. This information is used to evaluate the effectiveness of the current insulin dose and timing, identify the glucose nadir (lowest point), determine the duration of insulin action, and guide dose adjustments. Blood glucose curves may be performed in the veterinary clinic or at home using portable glucometers, with home monitoring often providing more representative results in cats prone to stress hyperglycaemia.
Considerations: In-clinic glucose curves may be affected by the stress of the hospital environment, potentially producing results that do not reflect the cat's typical glycaemic pattern at home. Home monitoring with ear-prick blood glucose measurements can overcome this limitation but requires owner training and a cat that tolerates the sampling procedure. Continuous glucose monitoring systems (small sensors adhered to the skin) are increasingly used in feline diabetes management, providing continuous glucose data over days to weeks without repeated blood sampling, though availability and cost vary.

Options & trade-offs

Management of feline diabetes mellitus centres on normalising blood glucose levels through a combination of insulin therapy, dietary modification, and addressing underlying contributors. The approach is shaped by the unique biology of feline diabetes, including the potential for remission and the importance of early, effective glycaemic control in preserving remaining beta cell function.

Insulin therapy

Subcutaneous insulin injections, typically administered twice daily, form the cornerstone of feline diabetes management. Several insulin types are used in cats, including protamine zinc insulin (PZI), glargine (a long-acting insulin analogue), and lente insulin, each with different duration of action and pharmacokinetic profiles in the feline species. The insulin dose is initially conservative and is gradually titrated upward based on clinical response and blood glucose monitoring results. The goal is to achieve blood glucose levels that remain within or close to the normal range for as much of the day as possible, while minimising the risk of hypoglycaemia (dangerous low blood glucose). Effective early insulin therapy, particularly with longer-acting insulins like glargine, may maximise the chance of achieving diabetic remission by rapidly resolving glucose toxicity and allowing surviving beta cells to recover function.

Trade-offs: Insulin therapy requires commitment to twice-daily injections at consistent times, which affects the owner's daily routine and travel flexibility. Learning injection technique, handling insulin appropriately (storage, mixing), and recognising signs of hypoglycaemia all require initial education and ongoing vigilance. The risk of hypoglycaemia — which can range from mild (wobbliness, increased appetite) to severe (seizures, collapse) — requires owner awareness and preparedness. Regular monitoring (blood glucose curves, fructosamine checks, clinical assessments) involves ongoing veterinary visits and associated costs. Individual cats respond differently to the same insulin type and dose, and finding the optimal regimen may involve a period of adjustment.

Dietary management

Dietary modification is a fundamental component of feline diabetes management, with evidence supporting the use of high-protein, low-carbohydrate diets that more closely approximate the macronutrient profile of a cat's natural prey diet. Reducing dietary carbohydrate content decreases the post-meal glucose surge, reducing the demand on the compromised beta cells and facilitating better glycaemic control. Commercially available prescription diabetic diets and many high-quality wet foods with high meat content provide appropriate macronutrient profiles. In overweight diabetic cats, a controlled weight loss programme is also incorporated, as even modest weight loss can improve insulin sensitivity and contribute to better glycaemic control and potentially remission.

Trade-offs: Transitioning a cat to a new diet requires patience, particularly in cats that are strongly habituated to their current food. Abrupt dietary changes may be refused, and gradual transition over days to weeks is generally more successful. The cost of prescription diabetic diets may be higher than standard cat food. In cats receiving insulin, dietary changes can alter insulin requirements, necessitating closer monitoring during the transition period. Weight loss must be gradual and controlled in cats (typically no more than 1-2% body weight per week) to avoid triggering hepatic lipidosis, a potentially life-threatening complication of rapid fat mobilisation in cats.

Oral hypoglycaemic agents

In some cats with mild diabetes or as part of a multimodal approach, oral hypoglycaemic medications may be considered. Glipizide, a sulfonylurea drug that stimulates insulin secretion from remaining functional beta cells, has been used in cats, though its efficacy is generally considered inferior to insulin therapy. Other oral agents such as metformin and acarbose have been evaluated in cats but are used less commonly due to side effects or limited efficacy. Oral agents may be considered in situations where insulin injections are not feasible or as a temporary measure while transitioning to injectable therapy.

Trade-offs: Oral hypoglycaemic agents are generally less effective than insulin therapy for achieving adequate glycaemic control in cats, and their use may delay resolution of glucose toxicity, potentially reducing the window of opportunity for remission. Glipizide can cause gastrointestinal side effects (vomiting, reduced appetite) in some cats and is only effective in cats that retain sufficient functional beta cell mass. There is some concern that sulfonylurea drugs may accelerate beta cell exhaustion and amyloid deposition through chronic stimulation, though this remains debated. Oral agents do not represent a 'simpler' alternative to insulin in most cases, as monitoring requirements remain similar.

Home monitoring programme

Home blood glucose monitoring using portable glucometers and ear-prick or paw-pad blood sampling allows owners to track their cat's blood glucose levels in a stress-free home environment. This approach provides more representative glycaemic data than in-clinic measurements in many cats, enabling more accurate dose adjustments and earlier detection of hypoglycaemic episodes or emerging remission. Continuous glucose monitoring systems, where a small sensor placed on the cat's skin provides continuous glucose readings transmitted to a smartphone app, represent an increasingly accessible advancement that provides detailed glycaemic data without repeated blood sampling. Home monitoring also enables owners to become more engaged in their cat's diabetes management and more adept at recognising patterns in glucose control.

Trade-offs: Home monitoring requires owner willingness to learn blood sampling techniques and the investment in monitoring equipment (glucometer, test strips, lancets, or continuous glucose monitor sensors). Not all cats tolerate ear-prick sampling, and some owners may feel anxious about the process initially. Interpretation of blood glucose data requires veterinary guidance, and isolated readings can be misleading without the context of the full clinical picture. Continuous glucose monitors involve periodic sensor replacement, adhesive application, and sensor costs that vary by system and availability. The data generated by home monitoring is most valuable when communicated to and interpreted by the veterinary team rather than used for independent dose adjustments by owners.

Common misconceptions

Misconception:

"Once a cat is diagnosed with diabetes, it will need insulin injections for the rest of its life."

Reality:

Unlike diabetes in dogs (which is predominantly immune-mediated and permanent), feline diabetes has a realistic potential for remission. Studies report that approximately 25-50% of newly diagnosed diabetic cats may achieve remission — a state where exogenous insulin is no longer required to maintain normal blood glucose levels — with prompt and effective management. The key factors that influence remission likelihood include early diagnosis and treatment, effective glycaemic control (which resolves glucose toxicity and allows surviving beta cells to recover), dietary modification to a low-carbohydrate diet, and achievement of healthy body weight. The window for remission may narrow the longer the diabetes remains poorly controlled, as progressive beta cell loss through amyloid deposition and sustained glucose toxicity can become irreversible. Cats that achieve remission require ongoing monitoring, as relapse can occur.

Misconception:

"Diabetes in cats is caused by feeding too many treats or too much sugar."

Reality:

While diet plays a role in feline diabetes — particularly through its contribution to obesity, which is the single most significant modifiable risk factor — the condition is not simply a result of eating 'too much sugar.' Cats are obligate carnivores with limited capacity for carbohydrate metabolism, and diets high in carbohydrates relative to protein may contribute to insulin resistance and obesity over time. However, the development of diabetes involves a complex interplay of genetic predisposition, body condition, physical activity levels, hormonal factors, and the unique feline predisposition to pancreatic islet amyloid deposition. Many obese cats never develop diabetes, and some cats of normal weight do develop the condition, highlighting that obesity is a risk factor rather than a sole cause.

Misconception:

"Giving insulin injections at home is too difficult and painful for the cat."

Reality:

While the prospect of administering twice-daily injections can seem daunting initially, most owners find that the process becomes routine relatively quickly, and most cats tolerate the injections remarkably well. Insulin is administered subcutaneously (under the skin) using very fine, short needles that cause minimal sensation — many cats show no reaction to the injection at all. The injection technique is straightforward once demonstrated by a veterinary professional, and the skin over the scruff of the neck and along the sides of the body provides accessible injection sites. The administration itself takes only seconds, and many owners develop the ability to incorporate it seamlessly into the feeding routine, as insulin is typically given at mealtimes.

Feline diabetes mellitus occupies a unique position among companion animal endocrine conditions, with the realistic potential for remission distinguishing it from diabetes in many other species. Understanding the interplay between insulin resistance, beta cell function, glucose toxicity, and the window of opportunity for remission provides valuable context for the management journey. The condition involves an ongoing relationship between monitoring, adjustment, and adaptation that evolves as the cat's needs change — whether moving toward remission, achieving stable long-term management, or navigating changes in insulin requirements over time.

Last reviewed: 24 April 2026 · Dr Alastair Greenway MRCVS