Diabetes and Cat Urine: How Diabetes Affects the Smell and Frequency of Feline Urination

Diabetes mellitus is one of the most common multifactorial metabolic diseases in cats, caused by endocrine pancreatic dysfunction, especially in adult and overweight cats.

It occurs when the body does not produce enough insulin or when its cells do not respond appropriately to insulin, preventing glucose from being absorbed from the blood.

There are multiple causes, including genetics, obesity, pancreatitis, adrenocortical hyperfunction, acromegaly, hyperthyroidism, glucocorticoids administered during infectious processes, kidney failure, heart disease, hyperlipidemia, islet amyloidosis, and other risk factors, including inactivity, neutering, and certain medications (such as megestrol acetate) that alter insulin sensitivity.

One of the first signs owners notice is changes in the urine, such as a darker colour, a fruity odour, and excessive urination.

It is vital to detect it early and determine its cause. In this way, appropriate treatment can be initiated promptly to prevent complications and achieve remission of the condition.

It is a lifelong disease, so good communication between veterinarians and pet owners is essential.

Understanding Feline Diabetes

Difference Between Type I and Type II Diabetes in Cats

There is no single criterion for classifying feline diabetes, so it is classified as Uncomplicated (without diabetic ketoacidosis) and Complicated (with diabetic ketoacidosis).

Because there is no standard criterion, human classification is used. It is then classified as type 1 diabetes and type 2 diabetes:

Type 1: the pancreas produces little or no insulin in response to an autoimmune or immune-mediated disease, and it is scarce in cats.
Type 2 (the most common in cats): insulin is produced, but the tissues do not respond adequately; that is, there is insulin resistance. This is mainly caused by obesity and physical inactivity.

So, how does insulin work in the feline body? What Happens When Glucose Levels Rise?

It is known that insulin, produced by the endocrine pancreas, lowers blood glucose levels (the amount of glucose in the blood) to maintain them within a normal range. In cats, this range is 80 to 120 mg/dL, and anything above 125 mg/dL is considered elevated (hyperglycemia).

In liver and muscle tissue, insulin allows glucose to enter cells to be used as energy or stored as glycogen, and it also inhibits or slows down the synthesis of more glucose.

In adipose tissue, it promotes triglyceride storage.

In protein metabolism, especially in muscle, it stimulates protein synthesis and inhibits protein catabolism (the breakdown of muscle cells).

However, when insulin is absent or tissue resistance develops, glucose accumulates in the blood. Approximately 20% of diabetic cats develop transient diabetes, usually occurring between the 4th and 6th week after diagnosis. In these cases, hyperglycemia, glucosuria, and clinical signs of diabetes resolve, and insulin treatment can be discontinued, but diet and other lifestyle changes to maintain normal glucose levels are continued.

How Diabetes Affects Urination

When blood glucose levels rise, they reach the kidneys, which are unable to reabsorb it, leading to glucose loss in the urine. This is called glucosuria, which directly affects urination and urine odour.

When excess glucose is eliminated, it draws water into the urine, causing:

• Increased urine volume (polyuria)

• Increased urinary frequency

• Increased water consumption (polydipsia). Increased urine volume decreases blood volume, triggering the thirst mechanism and leading to polydipsia.

These are the symptoms most commonly observed by caregivers and cause them alarm.

In the long term, diabetes can damage the kidneys, increasing the risk of chronic kidney disease.

Changes in the Smell of Cat Urine

Sweet or Fruity Odour

How does excess glucose alter the smell of urine?

The presence of glucose in urine gives it a characteristic fruity or sweet odour. If the sweet smell persists, it indicates diabetes, poorly controlled diabetes, or the need to adjust the insulin dose.

Strong, Unusual, or “Off” Smells

These symptoms can appear due to:

Secondary Urinary Tract Infections

When diabetes is not controlled, secondary infections increase due to decreased granulocytic function and delayed wound healing. One of the organs most affected by secondary infections is the kidney, as bacteria proliferate more readily in the presence of glucose in the urine.

Dehydration and Concentrated Urine

Glucose in the urine increases water loss by osmosis, leading to dehydration in our pet and, subsequently, to concentrated urine with a more pungent odour.

Ketone Production and Diabetic Ketoacidosis (DKA)

This is a medical emergency caused by serious complications of diabetes mellitus. When cells lack glucose due to insufficient insulin for its uptake or the cells’ inability to capture it, they begin to use fat stores for energy. This breakdown produces ketone bodies, which give our cat’s breath a smell similar to acetone or fermented fruit.

Changes in the Frequency of Urination

Polyuria: Why Diabetic Cats Urinate More Often?

Diabetic cats urinate more frequently and in larger volumes. This is due to the glucose being carried away by the body water lost through urine.

Large Volumes vs. Frequent Small Amounts

Large volumes. Typical of diabetes, caused by the presence of glucose in the urine, which draws out larger volumes of body water that are lost through urination, resulting in our cat urinating more frequently.

Frequent small amounts. Indicate infection, inflammation, or obstruction of the urinary tract, not necessarily diabetes.

Nighttime Urination (Nocturia)

Many owners notice their cat getting up to urinate at night. It’s important to distinguish between nighttime urination and urinary incontinence, the latter of which is common in neutered or spayed cats, obese cats, older cats, or those with sphincter dysfunction.

Nocturia, on the other hand, refers to the voluntary urge to urinate at night.

Increased Drinking as a Related Sign

It is a sign that almost always accompanies polyuria, due to a greater amount of water lost through urine.

Complications: When Urine Changes Signal an Emergency

Diabetic Ketoacidosis (DKA)

This is a serious condition caused by the accumulation of ketone bodies, which are produced when the body breaks down fats to provide energy, since glucose cannot be used by the body’s cells.

What Ketones Are

These are byproducts produced when the body uses fat as its primary energy source.

Symptoms: Acetone Odour, Lethargy, Vomiting, Rapid Breathing
- Strong acetone odour
- Severe lethargy
- Dehydration
- Vomiting
- Rapid or laboured breathing
Why Immediate Veterinary Care Is Critical

It requires immediate veterinary attention because our pet may have seizures, and it is often fatal.

Severe Dehydration

Reduced Skin Elasticity.

Loss of skin elasticity, which occurs when the cat, even though it is drinking more water, loses it through urine as it is washed out of the body by the concentration of glucose in it.

Dark, Concentrated Urine

Dark and highly concentrated urine (honey-colored), due to concentration from dehydration.

Risks Associated with Fluid Loss

Dry or sticky gums, due to dehydration.

The combination of polyuria and vomiting can rapidly dehydrate a diabetic cat.

Diagnosing Diabetes Through Urine and Blood Tests

Urine analysis, which is used to measure:

Glucose in urine, or glucosuria, is the presence of glucose in the urine. There should be no glucose in the urine. Urinary glucose occurs when blood glucose levels exceed 200-288 mg/dL (11-16 mmol/L), leading to glucose excretion in the urine. Cats under stress tend to have elevated blood glucose levels, but glucose is not present in the urine unless the stress is prolonged. In these cases, a blood fructosamine test should be performed.
Ketones, depending on the severity of diabetes. Ketone measurement is done with reagent strips and is a semi-quantitative test. Their presence indicates that the cat is using body fat to compensate for the energy lost from glucose.
Specific gravity or urine density (helps assess hydration and kidney function). Regarding the relative density of urine, it is usually 1.026-1.035 g/mL, as above.

Blood tests:

Blood glucose
- Normal range (fasting): 80 to 120 mg/dL
- Normal (after eating): May increase, but generally does not exceed 300 mg/dL in a healthy cat
- Level in a controlled diabetic cat: The goal is to maintain a range of 80 to 270 mg/dL to control symptoms
- Hypoglycemia (low glucose): Levels below 80 mg/dL. Levels below 40 mg/dL are life-threatening.
- Hyperglycemia (high glucose) in diabetic cats: Levels above 270 mg/dL may indicate diabetic ketoacidosis and require immediate veterinary attention.
Serum fructosamine:

In some cats, stress from movement, car transport, or visits to the veterinary hospital can raise blood glucose levels (stress hyperglycemia). When this condition is suspected, a blood fructosamine test is used. The normal range is 190-365 μmol/L. This test provides an average blood glucose reading over the past two weeks; an elevated reading is indicative of diabetes.

Rule out other causes of polyuria or frequent urination, such as kidney disease, hyperthyroidism, or urinary tract infections.

How Diabetes Treatment Improves Urinary Symptoms

Successful treatment aims to control, reduce, or eliminate clinical signs.

Type II diabetes mellitus (insulin resistance) in cats is insulin-dependent. Therefore, the cornerstone of treatment is insulin administration and dietary modifications.

Insulin Therapy

This is the mainstay of treatment and rapidly reduces glucosuria and polyuria. Cats are highly unpredictable in their response to diabetes treatments; therefore, treatment begins with insulin administration every 12 hours, monitored by measuring blood glucose to determine if adjustments to the insulin dosage or administration interval are necessary.

Dietary Modifications

Low-carbohydrate, high-protein diets help regulate glucose and improve insulin response.

In some cases, probiotics have been shown to help control diabetes. Therefore, some veterinarians recommend them in conjunction with high-protein, low-carbohydrate diets.

Hydration support

Offer plenty of fresh water or wet food.

Home monitoring

The owner will be asked to observe their cat’s litter box, measuring urine volume and odour, which will alert them to blood sugar imbalances. They should also learn how to use a glucometer at home to measure blood glucose levels and better manage diabetes, as other conditions can mask the proper response to insulin and diet.

When to Visit the Vet

We should take our cat to the vet if we notice any of the following symptoms:

Persistent sweet odour in the urine
Sudden increase in urination or water consumption.
Lethargy, vomiting, or weight loss.
Signs of a urinary tract infection.
Decreased physical activity.
Any signs of ketoacidosis (rapid breathing, lethargy, drowsiness).

It is essential to have regular checkups for diabetes to adjust insulin and diet, as some cats’ diabetes can stabilise, and diet alone may be sufficient to maintain their quality of life.

Conclusion

Diabetes mellitus is a disease with increasing prevalence in recent years due to changes in cats’ lifestyles, such as indoor living, a shift towards diets with a higher percentage of carbohydrates, reduced physical activity, a higher incidence of obesity, and increased life expectancy.

Cats are usually taken to the veterinarian only when clinical signs become evident and pose a problem for their owners. Therefore, at the time of diagnosis, all diabetic cats present with fasting hyperglycemia and glucosuria, regardless of the type of diabetes mellitus they may have.

Changes in urine are one of the earliest and most visible indicators of feline diabetes. Detecting them early allows initiation of appropriate treatment and prevention of serious complications. With proper management, regular monitoring, and continuous communication with the veterinarian, diabetic cats can lead long, comfortable, and healthy lives.

Therapy should be combined, including dietary control, physical activity, and, if necessary, medications such as insulin and hypoglycemic agents, and should be individualised for each patient. Due to the high incidence of Non-Insulin Dependent Diabetes Mellitus (Type II) and transient diabetes in cats and the effectiveness of treatment with diet and oral hypoglycemic agents, it would be helpful to differentiate Type I Diabetes from Type II Diabetes in advance.

Links for references:

– Ribas, P. J. (2023). Feline diabetes. Final degree project. Facultad de Veterinaria-Universidad de Zaragoza. pp.: 42. Fuente: https://zaguan.unizar.es/record/128986/files/TAZ-TFG-2023-3884.pdf?version=1
– Rondero Ramírez, I.L. (2013). Diagnosis, treatment, and control of diabetes mellitus in dogs and cats (Literature Review). Thesis submitted in partial fulfillment of the requirements for the degree of Doctor of Veterinary Medicine and Animal Science. Facultad de Estudios Superiores, Universidad Autónoma de México. P.p: 158. Fuente: https://tesiunamdocumentos.dgb.unam.mx/ptd2013/mayo/0694788/0694788.pdf?utm_source=chatgpt.com
– https://www.petmd.com
– https://www-thedrakecenter-com/resources/materials/cats/diabetes-mellitus-cats