Diabetes Mellitus

Diabetes mellitus occurs when the pancreas produces insufficient insulin (Type 1, the more common form in dogs) or when body tissues become resistant to insulin (Type 2). Without insulin, cells cannot use glucose properly - blood sugar rises, the body breaks down fat and muscle for energy, and a cascade of metabolic effects follow.

The classic presentation is increased thirst, increased urination, weight loss despite normal or increased appetite, and lethargy. Once diagnosed and stabilised on insulin, diabetic dogs can have excellent quality of life - but management requires daily commitment and detailed logging.

Daily monitoring essentials

Consistent routine is the foundation of diabetic management. Record every day:

Insulin administration:

• Time given
• Dose (in units)
• Which leg or site used (rotating injection sites prevents lipodystrophy)
• Whether the dog ate a full meal before the injection

Appetite and food intake:

• Whether the dog ate normally, partially, or refused food
• What was fed and the approximate amount

Water intake:

• Normal, increased, or decreased compared to baseline

General demeanour and energy level

Body weight - weigh weekly; note on the same scale at the same time of day

Glucose monitoring

Your vet will establish a target glucose range and a monitoring schedule. Options include:

• In-clinic glucose curves - a series of blood glucose measurements throughout the day to assess how well insulin is working over the dosing period
• Home glucose monitoring - using a pet glucometer (or a human glucometer with the ear vein); values differ between dogs and humans, so use a device validated for canine use or apply a conversion factor your vet provides
• Continuous glucose monitors (CGMs) - devices like the FreeStyle Libre can be used in dogs with veterinary guidance; they provide 24/7 glucose data and can reveal patterns that spot checks miss

Log every glucose reading with the time, the reading value, and where in the dosing cycle it was taken (e.g., 4 hours post-injection).

Signs of hypoglycaemia (low blood sugar)

Hypoglycaemia is a medical emergency. Signs include:

• Weakness, wobbling, or stumbling
• Muscle tremors or shaking
• Seizures
• Collapse
• Pale gums

If you suspect hypoglycaemia: rub a small amount of honey or corn syrup on the gums and contact your vet or emergency practice immediately. Do not give more insulin. Log the time, the circumstances, and whether the dog had eaten normally.

Signs of hyperglycaemia (high blood sugar) / diabetic ketoacidosis (DKA)

Persistently high blood sugar, particularly if the dog isn't eating, can progress to ketoacidosis - a serious complication. Signs include:

• Vomiting
• Lethargy
• Sweet-smelling or "pear drop" odour to the breath
• Rapid breathing
• Loss of appetite

DKA requires emergency veterinary treatment.

Diet and exercise consistency

Dietary consistency is as important as insulin consistency. Diabetic dogs should eat the same food, in the same amount, at the same times each day. Changes in food type, portion size, or feeding time directly affect insulin requirements.

Exercise also affects glucose levels. Consistent daily exercise is beneficial; unusually intense exercise can cause hypoglycaemia. Note any significant changes in activity level alongside glucose readings.

When to contact your vet

Go to the emergency vet immediately if:

• Your dog shows signs of hypoglycaemia (weakness, tremors, seizures, collapse)
• Signs of DKA are present (vomiting, sweet breath, lethargy, not eating)
• Your dog has had a seizure

Contact your vet same day if:

• Your dog has not eaten and you're unsure whether to give the usual insulin dose
• Glucose readings are consistently outside the target range
• Your dog is vomiting or has diarrhoea alongside insulin administration

Schedule a routine appointment for:

• Regular glucose curve assessments (frequency decreases as control improves)
• Fructosamine testing (a 2–3 week average of glucose levels)
• Any planned changes to dose or diet

Frequently Asked Questions

Should I give insulin if my dog hasn't eaten? Generally no - giving insulin to a dog who hasn't eaten risks dangerous hypoglycaemia. Contact your vet for specific guidance, as the answer may vary depending on the dog's situation and insulin type.

How do I give an insulin injection? Your vet or nurse will demonstrate technique at diagnosis. The basics: clean the injection site with a wipe, pinch a fold of skin (usually scruff or flank), insert the needle at 45 degrees, and inject slowly. Use a new needle each time. Rotate sites. Never reuse needles.

My dog seems well but glucose readings are high. Should I increase the dose? Don't adjust insulin doses independently. A consistently high glucose level warrants a vet consultation - the dose may need adjusting, but the method and timing of measurement, dietary factors, and other causes of insulin resistance should all be assessed first.

Can diabetes in dogs go into remission? Unlike cats, where remission is reasonably common, complete remission in dogs is rare. Dogs with secondary diabetes (caused by Cushing's disease, drugs, or pregnancy) may recover normal glucose regulation once the underlying cause is resolved. For most dogs with idiopathic diabetes, lifelong insulin treatment is necessary.

What is the life expectancy for a diabetic dog? Well-managed diabetic dogs can live for years after diagnosis with good quality of life. The prognosis is significantly affected by how well glucose is controlled and whether complications (cataracts are very common in diabetic dogs) are managed. Regular vet monitoring and owner commitment to daily logging make a substantial difference.