Hyperglycemia in dogs: diagnosis and treatment protocol

Safety: A sick dog with high glucose, vomiting, weakness, dehydration, abnormal breathing, or urine/blood ketones needs urgent veterinary admission. Insulin can rapidly cause fatal hypoglycemia or worsen potassium depletion if used incorrectly. The dose and protocol must be prescribed and monitored by a veterinarian.

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1. Common causes

A. Diabetes mellitus

• Middle-aged or older dog
• Female dog, especially an intact female in diestrus
• Obesity or insulin resistance
• Pancreatitis
• Hyperadrenocorticism (Cushing disease)
• Infection, especially urinary tract infection, dental disease, skin infection
• Drugs: glucocorticoids, progestagens, some diuretics
• Previous pancreatitis or pancreatic injury

B. Transient stress hyperglycemia

C. Drug-induced hyperglycemia

• Prednisone, dexamethasone, other corticosteroids
• Progestagens
• Drugs that promote insulin resistance or pancreatitis in susceptible patients

D. Other endocrine or metabolic disorders

• Cushing disease
• Acromegaly, uncommon in dogs
• Pheochromocytoma, rare
• Pancreatitis
• Severe systemic inflammation or sepsis

E. Diabetic emergencies

• Diabetic ketoacidosis (DKA): insulin deficiency plus ketone production and metabolic acidosis.
• Hyperosmolar hyperglycemic syndrome (HHS): extreme hyperglycemia and dehydration with high serum osmolality, often glucose >600 mg/dL, but little or no ketosis/acidosis. Merck Veterinary Manual

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2. Signs and symptoms

Typical signs of uncomplicated diabetes

Signs of DKA or severe decompensation

• Vomiting
• Anorexia or refusal to eat
• Marked lethargy, weakness, collapse
• Dehydration: tacky gums, sunken eyes, poor skin elasticity
• Abdominal pain, especially if pancreatitis is present
• Rapid or deep breathing
• Fruity or acetone-like breath, not always present
• Depression, altered behavior, stupor, coma

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3. Diagnostic protocol

Step 1: Confirm that hyperglycemia is persistent

1. Blood glucose
2. Urinalysis
   • glucose
   • ketones
   • specific gravity
   • sediment examination
3. Repeat blood glucose if stress, pain, or recent feeding could affect the result.

• Persistent hyperglycemia
• Glucosuria
• Compatible clinical signs
• Often increased serum fructosamine

Step 2: Use fructosamine

• High fructosamine: supports sustained hyperglycemia
• Normal fructosamine with one high glucose reading: consider transient/stress hyperglycemia or laboratory context

Step 3: Determine whether DKA or HHS is present

DKA is likely when there is:

• Hyperglycemia
• Ketonemia or moderate to large ketonuria
• Metabolic acidosis, usually low bicarbonate and low pH
• Systemic illness such as vomiting, anorexia, dehydration, weakness

HHS is likely when there is:

• Severe hyperglycemia, often >600 mg/dL
• High effective serum osmolality, usually >320 mOsm/kg
• Severe dehydration and neurologic abnormalities may occur
• No or only mild ketosis/acidosis in classic HHS

Step 4: Baseline tests before treatment

Calculations used in hospital

• Anion gap: detects unmeasured acids such as ketoacids.
• Corrected sodium: hyperglycemia lowers measured sodium by drawing water into blood.
• Effective osmolality: helps identify HHS and guides the safe speed of glucose correction.

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4. Treatment goals

1. Stop excessive drinking, urination, hunger, and weight loss.
2. Avoid hypoglycemia.
3. Achieve a safe glucose curve and acceptable average glycemia.
4. Treat infections and concurrent disease.
5. Prevent DKA, HHS, cataracts, and recurrent urinary infections.
6. Establish a routine the owner can follow consistently.

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5. Treatment of stable, uncomplicated diabetic hyperglycemia

A. Insulin is the main treatment

First-line maintenance insulin options

B. Feeding plan

• Feed two equal-calorie meals each day.
• Give each meal immediately before or at the time of the corresponding insulin injection.
• Keep meal type, amount, exercise, and injection time consistent.
• A high-quality complete diet is appropriate. Diet changes should be gradual and planned with the veterinarian.
• Weight reduction is useful for an obese dog, but should be controlled and not rapid.
• Do not give a full insulin dose to a dog that refuses food without immediate veterinary instructions.

C. Managing an intact female

D. Treat concurrent disease

• Urinary tract infection
• Dental infection
• Skin infection
• Pancreatitis
• Cushing disease
• Obesity
• Steroid medication exposure
• Incorrect injection technique, expired insulin, incorrect storage, or wrong syringe

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6. Monitoring and adjusting maintenance insulin

At home

• Water intake
• Urination volume/frequency
• Appetite
• Body weight weekly if possible
• Energy level
• Vomiting or diarrhea
• Injection time and dose
• Any suspected hypoglycemia episode
• Urine ketones, if advised by the veterinarian

At the clinic

• Recheck about 1-2 weeks after starting or changing insulin
• Blood glucose curve or validated home glucose monitoring
• Fructosamine periodically
• Weight and clinical signs
• Urinalysis/culture when infection is suspected
• Rechecks every 2-4 months after stabilization, individualized to the dog

When hyperglycemia persists, check before increasing insulin

1. Was insulin given at the right time and dose?
2. Is the correct syringe being used?
3. Is insulin stored and handled correctly?
4. Is the dog actually receiving the injection subcutaneously?
5. Is the dog eating consistent meals?
6. Is there hypoglycemia followed by rebound hyperglycemia?
7. Is insulin action too short?
8. Is there infection, pancreatitis, Cushing disease, obesity, or medication-related insulin resistance?

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7. Treatment of hypoglycemia caused by insulin

Warning signs

• Weakness, wobbliness, shaking
• Sudden hunger
• Restlessness, disorientation
• Seizures
• Collapse or unconsciousness

Immediate owner response

1. Offer food.
2. Rub a small amount of honey, corn syrup, or glucose gel on the gums.
3. Contact a veterinarian urgently.

• Rub glucose source on the gums only if it can be done safely.
• Do not force liquids or food into the mouth.
• Go to an emergency veterinary hospital immediately.

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8. DKA treatment protocol: veterinary hospital only

Treatment priorities

1. Restore circulation and correct dehydration
2. Correct potassium, phosphorus, and other electrolyte deficits
3. Start regular insulin after initial fluid stabilization
4. Correct ketosis and acidosis gradually
5. Treat the underlying trigger, such as pancreatitis, infection, or missed insulin
6. Monitor for cerebral edema, hypoglycemia, arrhythmia, and electrolyte shifts

A. IV fluids

• Isotonic crystalloid fluid therapy is used to restore perfusion and replace deficits.
• The exact fluid type, bolus, rate, deficit calculation, urine output, sodium trend, cardiac status, and kidney status must be individualized.
• Fluids often begin before insulin because they improve perfusion, lower glucose through dilution/renal excretion, and help correct dehydration.

B. Potassium and phosphorus

• Measure potassium repeatedly.
• Add potassium to IV fluids according to the current potassium concentration, ECG, urine production, and monitoring.
• Correct severe hypokalemia before or while cautiously beginning insulin, according to the attending veterinarian's protocol.
• Monitor phosphorus, magnesium, and acid-base status.

C. Regular insulin protocols

Option 1: Constant-rate infusion, CRI

• Add regular insulin 2.2 U/kg to 250 mL of 0.9% saline
• Adjust the infusion based on blood glucose every 1-2 hours
• Add dextrose as glucose declines
• Avoid a glucose fall greater than 50-100 mg/dL per hour to reduce neurologic risk. Merck DKA insulin table

Option 2: Intermittent intramuscular regular insulin

• 0.2 U/kg regular insulin IM initially
• Then 0.1 U/kg IM every 60 minutes
• Once glucose is <250 mg/dL, use 0.1-0.3 U/kg SC every 4-6 hours until control is obtained.
• Monitor glucose every 1-2 hours. Merck DKA management

D. Dextrose is added before glucose becomes normal

E. Additional medications as needed

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9. Hyperosmolar hyperglycemic syndrome, HHS

• Markedly high glucose, often >600 mg/dL
• Severe dehydration
• High serum osmolality, usually >320 mOsm/kg
• Neurologic signs may occur
• Usually little/no ketonemia or acidosis, though mixed DKA-HHS can occur

• Careful IV rehydration
• Slow correction of glucose and osmolality
• Electrolyte monitoring/replacement
• Low-dose regular insulin after fluid resuscitation
• Management of the precipitating disease

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Flow chart

DOG WITH HIGH BLOOD GLUCOSE
            |
            v
ASSESS URGENCY
- Vomiting?
- Not eating?
- Weakness/collapse?
- Dehydration?
- Deep/rapid breathing?
- Ketones?
            |
      +-----+------+
      |            |
      v            v
SICK / KETONES     STABLE DOG
OR NEURO SIGNS     WITH PU/PD, WEIGHT LOSS
      |            |
      v            v
EMERGENCY ADMISSION  CONFIRM PERSISTENT HYPERGLYCEMIA
      |              - Repeat glucose if needed
      |              - Urinalysis: glucose, ketones, infection
      |              - Fructosamine
      |              - CBC, chemistry, electrolytes
      v                         |
CHECK DKA vs HHS                 v
- Blood/urine ketones     DIABETES LIKELY?
- Blood gas, bicarbonate        |
- Electrolytes                  +------------------------+
- Anion gap                     |                        |
- Osmolality                    v                        v
      |                    YES: persistent           NO / UNCERTAIN:
      |                    hyperglycemia +            look for stress,
      |                    glucosuria/signs            drugs, pain, Cushing,
      |                         |                     pancreatitis, infection
      v                         |
DKA: acidosis + ketones         v
HHS: >600 mg/dL,                START LONG-TERM PLAN
high osmolality, little          - insulin
ketosis/acidosis                 - equal twice-daily meals
      |                          - owner training
      v                          - treat concurrent illness
HOSPITAL TREATMENT                    |
- IV fluids                           v
- Potassium/phosphorus         MONITOR AND ADJUST
- Regular insulin CRI or IM     - glucose curve/home checks
- Add dextrose as glucose falls - fructosamine
- Monitor glucose q1-2 h        - body weight, PU/PD
- Treat pancreatitis/infection  - urine ketones/infection
      |                                |
      v                                v
WHEN EATING, HYDRATED,           IF CONTROL POOR:
KETONES RESOLVING,               - verify dose/syringe/technique
AND STABLE:                      - assess hypoglycemia rebound
TRANSITION TO SC                 - find infection/pancreatitis/
MAINTENANCE INSULIN                Cushing/medication effects

When to seek emergency care today

• Vomiting or cannot keep water down
• Refusal of food
• Moderate/large urine ketones
• Weakness, collapse, seizure, confusion, or coma
• Deep/rapid breathing
• Severe dehydration
• Blood glucose persistently very high with illness signs
• Any suspected insulin overdose or hypoglycemia