Insulin
Insulin (Regular, Lispro, Isophane/NPH, Protamine Zinc/PZI, Porcine Zinc/Lente, Glargine, Detemir)
Also known as: Vetsulin · Caninsulin · ProZinc · Humulin · Novolin · Lantus · Levemir · Humalog · Regular insulin · NPH · PZI · Lente · Glargine · Detemir · Lispro · Crystalline Zinc Insulin · Isophane Insulin
Reviewed by the VetSheet Veterinary TeamUpdated Apr 5, 2026Evidence-based veterinary reference
Doses are a clinical reference for licensed veterinary professionals. Always confirm against the current label and the individual patient.
Dosing by species
🌎 NA — North America🌍 EU — Europe
Dogs
| Indication | Dose | Route | Frequency | Duration | Region |
|---|---|---|---|---|---|
| Diabetic ketoacidosis (Intermittent IM technique) | 0.2 Units/kg IM into muscles of the rear legs; repeat IM doses of 0.1 Units/kg hourly. As blood glucose approaches 250 mg/dL, switch to IM regular insulin at 0.1-0.3 Units/kg q4-6h or subcutaneous q6-8h. | IM, SC | hourly, then q4-8h | Until stabilized | 🌎 NA |
| Diabetic ketoacidosis (Constant Low-Dose Infusion) | 2.2 Units/kg regular insulin added to 250 ml of 0.9% sterile saline. Adjust infusion rate based upon hourly blood glucose determinations. Once blood glucose approaches 250 mg/dL switch to IM regular insulin every 4-6 hours or SC at 0.1-0.4 Units/kg q6-8h. | IV, then IM/SC | CRI, then q4-8h | Until stabilized | 🌎 NA |
| Severe hyperkalemia (>8 mEq/L) | 0.25-0.5 Units/kg slow IV bolus followed by 50% dextrose (4 mL/U of administered insulin); OR 0.5-1 Units/kg in parenteral fluids plus 2 grams dextrose per unit insulin administered | IV | Once | — | 🌎 NA |
| Uncomplicated diabetes mellitus (Vetsulin) | 0.5 Units/kg SC once daily concurrently with or right after a meal. If twice daily treatment is initiated, the two doses should be 25% less than the once daily dose. Alternatively: 0.5 Units/kg SC twice daily. | SC | q24h or q12h | Lifelong | 🌎 NA |
| Uncomplicated diabetes mellitus (NPH or Lente) | 0.25 Units/kg twice a day | SC | q12h | Lifelong | 🌎 NA |
| Uncomplicated diabetes mellitus (Glargine) | 0.25-0.5 Units/kg SC q12h | SC | q12h | Lifelong | 🌎 NA |
| Uncomplicated diabetes mellitus (Detemir) | 0.1-0.2 Units/kg SC q 12 hours | SC | q12h | Lifelong | 🌎 NA |
- Diabetic ketoacidosis (Intermittent IM technique): Initial doses may be reduced by 25-50% in animals with severe hypokalemia. Goal is to slowly lower blood glucose to 200-250 mg/dL over 6-10 hours.
- Diabetic ketoacidosis (Constant Low-Dose Infusion): Run approx 50 mL of insulin-containing fluid through drip set prior to administration to saturate binding sites.
- Severe hyperkalemia (>8 mEq/L): Use Regular insulin only.
- Uncomplicated diabetes mellitus (NPH or Lente): Initial insulin of choice for establishing control.
- Uncomplicated diabetes mellitus (Glargine): Used in poorly-controlled dogs where NPH/Lente are ineffective due to short duration.
- Uncomplicated diabetes mellitus (Detemir): Note the lower starting dose; canine receptors are 4x more sensitive to detemir than human receptors.
Cats
| Indication | Dose | Route | Frequency | Duration | Region |
|---|---|---|---|---|---|
| Diabetic ketoacidosis (Regular insulin) | Same protocol using regular insulin as described for dogs | IM, IV, SC | Varies | Until stabilized | 🌎 NA |
| Diabetic ketoacidosis (Glargine) | 2 Units per cat SC and 1 Unit per cat IM (regardless of body weight) initially; repeat the IM dose 4 or more hours later if BG > 250-290 mg/dL; repeat the SC dose every 12 hours. | SC and IM | Initially, then q12h SC | Until stabilized | 🌎 NA |
| Severe hyperkalemia | 0.5 to 1 Unit/kg IM regular insulin plus 2 grams dextrose per unit of insulin IV | IM | Once | — | 🌎 NA |
| Uncomplicated diabetes mellitus (Glargine, Detemir, or PZI) | Blood glucose <360 mg/dL: 0.25 Units/kg of ideal body weight SC every 12 hours; Blood glucose >=360 mg/dL: 0.5 Units/kg of ideal body weight SC every 12 hours | SC | q12h | Lifelong | 🌎 NA |
| Uncomplicated diabetes mellitus (ProZinc) | 0.2-0.7 Units/kg SC every 12 hours given concurrently with or right after a meal | SC | q12h | Lifelong | 🌎 NA |
| Uncomplicated diabetes mellitus (Vetsulin) | 0.5 Units/kg SC once daily | SC | q24h | Lifelong | 🌎 NA |
| Uncomplicated diabetes mellitus (Lente) | 1 Unit per cat SC twice daily for cats <4kg & 1.5-2 Units/cat twice daily for cats >4kg. Alternatively: 0.25 Units/kg SC twice daily if BG 216-342 mg/dL; 0.5 Units/kg SC twice daily if BG>360mg/dL. | SC | q12h | Lifelong | 🌎 NA |
- Uncomplicated diabetes mellitus (Glargine, Detemir, or PZI): If no monitoring in first week, begin with 1 Unit per cat every 12 hours.
- Uncomplicated diabetes mellitus (ProZinc): Goal: glucose nadir between 80 & 150 mg/dL.
Ferrets
| Indication | Dose | Route | Frequency | Duration | Region |
|---|---|---|---|---|---|
| Diabetes mellitus | 0.5-1 Unit per ferret SC twice daily. Alternatively: 0.1-0.5 Units/kg IM or SC twice daily to start; adjust to optimal dose. | SC, IM | q12h | Lifelong | 🌎 NA |
- Diabetes mellitus: May require insulin to be diluted.
Birds
| Indication | Dose | Route | Frequency | Duration | Region |
|---|---|---|---|---|---|
| Diabetes mellitus | Initially, 0.1-0.2 Units/kg regular insulin. When stabilized, NPH insulin can be started. Dose range is 0.067-3.3 Units/kg IM every 12-24 hours. | IM | q12-24h | Lifelong | 🌎 NA |
- Diabetes mellitus: Highly variable dose needed. Monitor for hypoglycemia.
Horses
| Indication | Dose | Route | Frequency | Duration | Region |
|---|---|---|---|---|---|
| Diabetes mellitus | 0.51 Unit/kg of PZI insulin OR 0.15 Units/kg IM or SC twice daily | IM, SC | q12h | As needed | 🌎 NA |
| Hyperlipemia in ponies | For a 200 kg pony: PZI 30 Units (total dose) IM every 12 hours on odd days (given with 100 grams glucose orally once daily); PZI 15 Units (total dose) IM every 12 hours on even days (given with 100 grams galactose orally once daily) | IM | q12h | Until hyperlipemia resolves | 🌎 NA |
- Diabetes mellitus: True DM is rare; mostly secondary to pituitary tumors (insulin-resistant).
Cattle
| Indication | Dose | Route | Frequency | Duration | Region |
|---|---|---|---|---|---|
| Adjunctive treatment of ketosis | 200 Units (total dose) SC once every 48 hours | SC | q48h | As needed | 🌎 NA |
- Adjunctive treatment of ketosis: Using PZI insulin.
Doses are a clinical reference for licensed veterinary professionals. Always confirm against the current label and the individual patient.
Overview
Insulin is a critical peptide hormone produced by the beta cells of the pancreatic islets of Langerhans. It is the cornerstone of therapy for diabetes mellitus and diabetic ketoacidosis (DKA) in veterinary medicine.
Formulations are broadly categorized by their onset and duration of action:
- Short-acting (Regular, Lispro): Used primarily in hospital settings for acute stabilization of DKA or severe hyperkalemia. Regular insulin is the only formulation that can be administered intravenously.
- Intermediate-acting (NPH, Lente/Porcine Zinc): Commonly used for maintenance therapy in dogs. Porcine insulin is structurally identical to canine insulin, minimizing the risk of anti-insulin antibody formation.
- Long-acting (PZI, Glargine, Detemir): Frequently used for maintenance therapy in cats, who metabolize insulin more rapidly than dogs.
Clinical Pearl: Feline diabetes often resembles human Type 2 DM and may go into remission with early, aggressive use of long-acting insulins (like glargine) combined with a low-carbohydrate diet. Canine diabetes is typically akin to human Type 1 DM, requiring lifelong exogenous insulin therapy.
Mechanism of action
Insulin initiates its action by binding to the tyrosine kinase insulin receptor on the cell membrane.
Mechanism Pathway: Receptor binding → Autophosphorylation → Activation of Insulin Receptor Substrates (IRS) → Activation of the PI3K/Akt pathway → Translocation of GLUT4 transport proteins to the cell surface → Rapid facilitated diffusion of glucose into skeletal muscle and adipose tissue.
Metabolic Effects:
- Carbohydrate metabolism: Promotes cellular glucose uptake and hepatic glycogenesis; inhibits glycogenolysis and gluconeogenesis.
- Lipid metabolism: Stimulates lipogenesis and potently inhibits lipolysis and ketogenesis (crucial for resolving DKA).
- Protein metabolism: Increases amino acid uptake and protein synthesis.
- Electrolyte shift: Drives potassium and magnesium into the intracellular space (utilized therapeutically for life-threatening hyperkalemia).
Safety & warnings
Contraindications
- Episodes of hypoglycemia (absolute contraindication)
- Systemic allergy to pork or pork products (specifically for Vetsulin/porcine lente)
Adverse effects
- Hypoglycemia (most common and potentially life-threatening)
- Insulin-induced hyperglycemia ('Somogyi effect' due to counter-regulatory hormone release following hypoglycemia)
- Insulin antagonism or resistance
- Rapid insulin metabolism
- Local hypersensitivity reactions to 'foreign' proteins
- Lipodystrophy at the injection site (if sites are not rotated)
Precautions
Because there are no alternatives for insulin in diabetic indications, there are no absolute contraindications except during hypoglycemia.
- Antibody Formation: Beef/pork insulin produces antibody formation in ~45% of dogs, leading to erratic control. Pork insulin is identical to canine insulin and is preferred. Cats have a low incidence of antibody production regardless of source.
- Injection Site: Do not inject at the exact same site day after day to prevent lipodystrophic reactions.
- Prescription Safety: Do NOT abbreviate Units as 'U', as it significantly increases the rate of transcription and fatal dosage errors (often misread as a zero).
Drug interactions
Can have variable effects on glycemic control and can mask the clinical signs associated with hypoglycemia.
Can mask the signs associated with hypoglycemia.
Insulin alters serum potassium levels; concurrent use requires close monitoring for cardiac arrhythmias, especially with concurrent diuretics.
May potentiate the hypoglycemic activity of insulin.
May decrease the hypoglycemic activity of insulin (cause insulin resistance).
Monitoring
- Blood glucose (serial curves or continuous monitoring)
- Patient weight
- Appetite and water intake
- Urine output
- Blood or urine ketones (if DKA suspected)
- Fructosamine (goal <450 micromol/L) or glycosylated hemoglobin
Pharmacokinetics
Half-life
Absorption
Varies widely by formulation. Regular insulin has immediate onset IV, and rapid onset (10-30 mins) IM/SC. Intermediate (NPH/Lente) and long-acting (PZI/Glargine/Detemir) formulations form microprecipitates or bind to tissues to delay absorption and prolong effect.
Distribution
Distributed widely throughout the body. Affects primarily liver, muscle, and adipose tissues.
Metabolism
Metabolized mainly by the liver and kidneys (also muscle and fat to a lesser degree) by enzymatic reduction to form peptides and amino acids. About 50% of insulin reaching the liver via the portal vein is destroyed.
Elimination
Filtered by the renal glomeruli and reabsorbed by the tubules, which also degrade it. Severe renal impairment affects clearance more than hepatic disease.
Overdose
Overdosage of insulin leads to hypoglycemia, which can be rapidly fatal or cause permanent brain damage if untreated.
Clinical Signs:
- Weakness, lethargy, ataxia
- Shaking, muscle fasciculations
- Head tilting, bizarre behavior, blindness
- Restlessness, extreme hunger
- Seizures and coma
Treatment:
- Mild: Offer the animal its usual food.
- Severe (e.g., seizures): Rub oral dextrose solutions (e.g., Karo® syrup) on the oral mucosa (do not pour down the throat to avoid aspiration).
- Veterinary Intervention: Intravenous injections of 50% dextrose solutions (small amounts, slowly administered—usually 2-15 mL).
- Monitoring: Once alleviated (usually within 1-2 minutes), monitor closely with serial blood glucose levels to prevent recurrence (especially with long-acting insulins) and adjust future doses.
Available products
Formulations
- Regular (Crystalline Zinc) injection
- Lispro injection
- Isophane (NPH) suspension
- Protamine Zinc (PZI) suspension
- Porcine Zinc (Lente) suspension
- Glargine injection
- Detemir injection
Veterinary
- Vetsulin (Porcine insulin zinc suspension 40 Units/mL)
- Caninsulin (Porcine insulin zinc suspension 40 Units/mL - Canada/Europe)
- ProZinc (Protamine zinc recombinant human insulin 40 Units/mL)
Human-labeled
- Humulin R / Novolin R (Regular 100 Units/mL)
- Humalog (Lispro 100 Units/mL)
- Humulin N / Novolin N (NPH 100 Units/mL)
- Humulin 70/30 / Novolin 70/30 (NPH/Regular mixture 100 Units/mL)
- Humulin 50/50 (NPH/Regular mixture 100 Units/mL)
- Lantus (Glargine 100 Units/mL)
- Levemir (Detemir 100 Units/mL)
Regulatory status
No regulatory data for: 🇺🇸 US · 🇪🇺 EU · 🇬🇧 UK · 🇭🇰 HK · 🇹🇼 TW · 🇯🇵 JP · 🇰🇷 KR · 🇦🇺 AU
Storage & stability
Store in the refrigerator (36-46°F / 2-8°C). Do not freeze. Avoid direct sunlight and extreme heat. Regular and NPH insulin may be stored in plastic syringes under refrigeration for up to 28 days. Glargine (Lantus) officially has a 28-day discard date at room temp, but clinical reports indicate opened vials stored in the refrigerator can be used for up to 6 months (discard if discolored). Detemir (Levemir) has a 42-day discard date.
Client information
Managing a diabetic pet requires commitment, but it becomes a routine part of daily life. Here are critical points for success:
- Storage: Keep insulin in the refrigerator. Do not freeze it or leave it in a hot car, as extreme temperatures destroy the protein. Allow the drawn-up syringe to reach room temperature before injecting to reduce discomfort.
- Handling the Vial: Gently roll the vial between your palms to mix it. Do not shake vigorously (unless specifically instructed by your vet for certain brands like Vetsulin), as this can damage the insulin molecules.
- Syringe Safety: Always use the correct syringe! U-40 syringes (red cap) are for U-40 insulin (like Vetsulin or ProZinc). U-100 syringes (orange cap) are for U-100 insulin (like Glargine or NPH). Mixing these up can cause a fatal overdose.
- Injection Technique: Give the injection under the skin (subcutaneously). Rotate injection sites daily (e.g., left side of chest, right side of chest, left flank, right flank) to prevent hard lumps from forming under the skin, which block insulin absorption.
- Hypoglycemia (Low Blood Sugar): This is an emergency. Watch for weakness, stumbling, trembling, staring into space, or seizures. If this happens, immediately rub Karo syrup (corn syrup) or honey on your pet's gums and call your veterinarian. Do not put your fingers in a seizing pet's mouth.
- Travel: When flying, keep insulin in your carry-on. A single pass through the X-ray is fine, but avoid repeated exposures.
VetSheet drug reference is intended for licensed veterinary professionals as a clinical decision-support aid, not a substitute for professional judgement or the manufacturer’s current label.