Vetsulin is a prescription intermediate-acting insulin manufactured by Merck Animal Health, FDA-approved for the treatment of diabetes mellitus in dogs (and cats). It contains purified porcine (pig-derived) insulin zinc suspension, which is a mixture of approximately 30% amorphous (short-acting) and 70% crystalline (longer-acting) insulin. This combination provides both a relatively rapid onset and an intermediate duration of action, mimicking the body’s natural insulin response more closely than single-phase insulins. Porcine insulin is structurally identical to canine insulin, making Vetsulin the preferred initial insulin choice for most diabetic dogs.
What Is Vetsulin Used For?
Vetsulin is prescribed for the management of:
- Diabetes mellitus in dogs, the most common endocrine disorder in middle-aged to older dogs
- Hyperglycemia and associated clinical signs including excessive thirst (polydipsia), excessive urination (polyuria), increased appetite (polyphagia), and weight loss
The goal of insulin therapy is to control blood glucose levels sufficiently to resolve clinical signs and prevent diabetic complications such as diabetic ketoacidosis (DKA), cataracts, and recurrent infections. Consult your veterinarian for proper diagnosis and monitoring.
Dosage
The recommended starting dose of Vetsulin is 0.5 IU/kg (0.25 IU/lb) subcutaneously twice daily, administered at the time of feeding. Your veterinarian will adjust the dose based on serial blood glucose curves and clinical response.
| Dog’s Weight | Starting Dose (0.5 IU/kg BID) | Administration |
|---|---|---|
| 10 lbs (4.5 kg) | 2-3 IU twice daily | Subcutaneous injection |
| 20 lbs (9 kg) | 4-5 IU twice daily | Subcutaneous injection |
| 40 lbs (18 kg) | 9 IU twice daily | Subcutaneous injection |
| 60 lbs (27 kg) | 13-14 IU twice daily | Subcutaneous injection |
| 80 lbs (36 kg) | 18 IU twice daily | Subcutaneous injection |
Vetsulin is available as a 40 IU/mL suspension in 10 mL vials. It must be used with U-40 insulin syringes or the VetPen (U-40 dosing pen). Do not use U-100 syringes, as this will result in significant dosing errors. Gently roll the vial (do not shake vigorously) until a homogeneously milky suspension is achieved before each use. Administer injections subcutaneously, rotating injection sites. Feed your dog a consistent diet at the same times each day.
Side Effects
| Common Side Effects | Serious Side Effects (Contact Your Vet Immediately) |
|---|---|
| Mild hypoglycemia (mild lethargy, slight trembling) | Severe hypoglycemia (seizures, collapse, unresponsiveness) |
| Injection site irritation | Persistent vomiting or diarrhea |
| Transient appetite changes | Diabetic ketoacidosis (lethargy, vomiting, fruity breath) |
| Somogyi rebound (rebound hyperglycemia from insulin overdose) |
Hypoglycemia is the most dangerous potential complication of insulin therapy. Signs include weakness, trembling, disorientation, staggering, seizures, and collapse. If you suspect hypoglycemia, rub corn syrup or honey on your dog’s gums immediately and contact your veterinarian. Always keep a fast-acting glucose source readily available.
Drug Interactions
- Corticosteroids (prednisone, dexamethasone): Increase blood glucose and may antagonize insulin effect; dose adjustments may be needed.
- Progestins and growth hormone: Can cause insulin resistance.
- Beta-blockers: May mask signs of hypoglycemia.
- Anabolic steroids: May increase insulin sensitivity, raising hypoglycemia risk.
- Other hypoglycemic agents: Use with caution; may potentiate hypoglycemia.
Always inform your veterinarian of all medications, supplements, and dietary changes.
Contraindications
Vetsulin should not be used in:
- Dogs with known hypersensitivity to porcine insulin or any product component
- During episodes of active hypoglycemia
Use with caution in dogs with concurrent illness (infection, pancreatitis, Cushing’s disease, hypothyroidism) as these conditions can affect insulin requirements. Your veterinarian will address comorbidities to optimize diabetic management.
Storage
- Store unopened vials refrigerated at 35-46 degrees F (2-8 degrees C).
- Opened vials: store refrigerated and use within 42 days of first puncture.
- Do not freeze. Discard if frozen.
- Protect from light and extreme heat.
- Keep out of reach of children and pets.
Frequently Asked Questions
How do I give my dog insulin injections? Your veterinarian or veterinary technician will demonstrate proper injection technique. Inject subcutaneously (under the skin) along the scruff of the neck or side of the chest, rotating sites. Most dogs tolerate injections very well with practice. Consult your veterinarian if you have questions about technique.
What if my dog does not eat before an injection? If your dog skips a meal or eats significantly less than usual, do not give the full insulin dose without consulting your veterinarian. Giving insulin without adequate food intake increases the risk of hypoglycemia. Your veterinarian will provide guidance for missed or reduced meals.
How often does my dog need blood glucose monitoring? Your veterinarian will recommend periodic blood glucose curves (serial glucose measurements over 12-24 hours) to assess insulin effectiveness and adjust dosing. Initially, curves may be done every 1-2 weeks, then less frequently once stable. Home glucose monitoring may also be recommended. Consult your veterinarian.
Can my diabetic dog live a normal life? With consistent insulin therapy, appropriate diet, regular monitoring, and veterinary care, many diabetic dogs live comfortable, active lives for years after diagnosis. Commitment to a routine is essential for successful management.
Why does Vetsulin require U-40 syringes? Vetsulin is a U-40 insulin (40 units per mL), whereas most human insulins are U-100 (100 units per mL). Using U-100 syringes with Vetsulin will result in an underdose, potentially causing dangerous hyperglycemia. Always use U-40 syringes or the VetPen.
This content is for informational purposes only and is not a substitute for professional veterinary advice. Always consult your veterinarian before starting, changing, or stopping any medication for your dog.