Insulin: veterinary dose and monograph

At a glance

Drug class

Veterinary drug

Also known as

Caninsulin, Vetsulin, Lantus (glargine), ProZinc (PZI), NPH

Species with doses

Dogs, Cats, Horses, Birds and Ferrets

Routes

SC, IM, IV

Last reviewed

1 October 2026

Indications

• Canine diabetes mellitus
• Feline diabetes mellitus
• Diabetic ketoacidosis (regular / soluble insulin, separate protocol)

Insulin dose by species

Doses are per administration unless stated. mg/kg doses scale with body weight; per-animal, per-quarter and infusion-rate doses are shown as the reference writes them.

Dogs

• Diabetes (lente / NPH start): Doses in UNITS/kg. Plumb’s p.648: NPH or porcine lente about 0.25 U/kg SC twice daily (Nelson 2006); Vetsulin label 0.5 U/kg SC once daily with or after a meal — if twice daily is needed, each dose is 25% less than the once-daily dose; 0.5 U/kg twice daily (Bruyette 2010). Papich 5e: Vetsulin 0.5 U/kg once or twice daily; NPH 1 U/kg q12–24h under 15 kg, 0.5 U/kg over 25 kg. Adjust by 10–25% steps on glucose curves; use U-40 syringes for 40 U/mL insulin.
• Diabetes — glargine: Units/kg. Plumb’s p.648 (Fracassi 2010): 0.25–0.5 U/kg SC q12h. Papich 5e: start 0.3 U/kg q12h; well-regulated dogs 0.32–0.67 U/kg q12h. Usually reserved for dogs poorly controlled on NPH/lente.
• Diabetes — detemir: Units/kg. Plumb’s p.648 (Ford 2010): 0.1–0.2 U/kg SC q12h — dogs are about 4× more sensitive to detemir than people. Papich 5e: 0.12–0.25 U/kg q12h; diluent may be needed in small dogs.
• Diabetic ketoacidosis — regular insulin IM: Units/kg, REGULAR insulin only. Plumb’s p.648 (Nelson): 0.2 U/kg IM initially, then 0.1 U/kg IM hourly, aiming to lower glucose to 200–250 mg/dL over 6–10 h; reduce the first doses by 25–50% if severely hypokalaemic; then 0.1–0.3 U/kg IM q4–6h with 5% dextrose. Papich 5e: over 10 kg 0.25 U/kg then 0.1 U/kg hourly IM. Fluids and potassium first.

Cats

• Diabetes (glargine / PZI start): Units/kg of IDEAL body weight. Plumb’s p.648 (Rand 2010): glargine, detemir or PZI 0.25 U/kg q12h if glucose <360 mg/dL, 0.5 U/kg q12h if ≥360 mg/dL; 1 U per cat q12h if not monitored in the first week; ProZinc label 0.2–0.7 U/kg q12h with a meal. Papich 5e: glargine 0.5 U/kg q12h; PZI 0.2–0.7 U/kg q12h (or 1–2 U per cat). Target nadir 80–150 mg/dL.
• Diabetic ketoacidosis — regular insulin IM: Units/kg, REGULAR insulin. Papich 5e: 0.2 U/kg IM initially, then 0.1 U/kg IM hourly until glucose is under 300 mg/dL, then 0.25–0.4 U/kg SC q6h. Plumb’s p.648: same protocol as dogs; glargine alternative 2 U per cat SC plus 1 U per cat IM (Rand 2010).

Horses

• Hyperlipaemia / pituitary hyperglycaemia: Units/kg. Plumb’s p.650 (Robinson 1987): PZI 0.15 U/kg IM or SC twice daily. True equine diabetes mellitus is rare.
• Hyperkalaemia (regular insulin CRI): Papich 5e: regular insulin 0.1–0.2 U/kg/h IV with 5% dextrose (e.g. 0.5 mL of 100 U/mL insulin in 5 L fluids containing 500 mL of 50% dextrose, given over 1 h). Monitor glucose and potassium.

Birds

• Diabetes mellitus: Units/kg. Plumb’s p.650 (Oglesbee 2003): start 0.1–0.2 U/kg; NPH doses of 0.067–3.3 U/kg IM q12–24h have been reported. Titrate with glucose curves; watch for hypoglycaemia.

Ferrets

• Diabetes mellitus (uncommon; often post-insulinoma-surgery): Units/kg. Plumb’s p.650: 0.1–0.5 U/kg IM or SC twice daily to start (Williams 2000); NPH 0.5–1 U per ferret SC twice daily (Quesenberry & Carpenter 2003). Goal: negative urine ketones with trace glucose. Dilute for accurate dosing.

Contraindications

Active hypoglycaemia. Never share a needle / syringe type between U-40 and U-100 products (dosing error). Do not shake glargine; gently roll lente / PZI.

Species-specific warnings

Cats: Roll (do not shake) PZI / lente insulins; handle glargine gently. Start low — cats are exquisitely sensitive to over-dosing.

Adverse effects

• Hypoglycaemia — weakness, ataxia, seizures, collapse
• Somogyi rebound hyperglycaemia from over-dosing
• Local injection reaction; insulin resistance with concurrent disease

Drug interactions

• Corticosteroids, progestagens, growth hormone: induce insulin resistance — raise the dose requirement
• Beta-blockers: mask the adrenergic warning signs of hypoglycaemia and can prolong it
• Other glucose-lowering agents: additive hypoglycaemia
• Infection or dioestrus (intact bitch): marked insulin resistance — expect higher needs

Monitoring

• Blood-glucose curve 7–14 days after each dose change (or continuous glucose monitor)
• Water intake, bodyweight, appetite, urine glucose / ketones
• Fructosamine every few months for longer-term control

Toxicity and overdose

The dangerous toxicity is HYPOGLYCAEMIA — lethargy, tremor, ataxia, disorientation, seizures and coma — from overdose, reduced food intake, or improving glycaemic control. Somogyi (rebound) hyperglycaemia from over-dosing mimics under-dosing and is a classic pitfall.

Management: Conscious hypoglycaemia: feed or rub oral glucose / honey onto the gums. Obtunded or seizing: IV 50 % dextrose 0.5–1 mL/kg (diluted) then a dextrose CRI; withhold the next insulin dose, monitor glucose closely, and re-evaluate the protocol (often halve the dose).

Clinical pearls

• Match the syringe to the insulin: U-40 insulin needs U-40 syringes, U-100 needs U-100 — a mismatch is a 2.5× dosing error
• Cats started promptly on glargine / PZI plus a low-carb diet have a real shot at diabetic remission
• When in doubt about a dose, under-dose — hypoglycaemia kills faster than a day of hyperglycaemia

Mechanism of action

Hormone replacement. Binds the insulin-receptor tyrosine kinase, driving glucose uptake (GLUT4) into muscle and fat, hepatic glycogen synthesis, and suppression of gluconeogenesis and lipolysis — lowering blood glucose and reversing the catabolic state of diabetes. Lente / NPH are intermediate-acting; glargine / PZI are long-acting, near-peakless basal insulins.

Formulations and products

• Caninsulin / Vetsulin 40 IU/mL (porcine lente)
• Insulin glargine 100 IU/mL (Lantus)
• PZI 40 IU/mL (ProZinc, feline)
• NPH 100 IU/mL (human isophane)
• Caninsulin / Vetsulin (MSD Animal Health) — 40 IU/mL porcine lente, SC injection
• ProZinc (Boehringer Ingelheim) — 40 IU/mL protamine zinc, SC injection
• Lantus (glargine) — 100 IU/mL, SC injection / pen (human-label)
• Huminsulin — NPH / Regular, 40 & 100 IU/mL, SC injection (human-label)
• Basalog (glargine) — 100 IU/mL, SC injection / pen (human-label)

Storage

Refrigerate 2–8 °C; do not freeze. Roll lente / PZI gently to resuspend (never shake); handle glargine gently. Discard opened vials per label (≈28–42 days) and avoid temperature extremes.

Before you use this dose

Reference doses for veterinary professionals. Confirm the dose against the product label, the patient’s condition, current guidance and local regulations before use; the attending veterinarian remains responsible for every clinical decision.

Other hormones, emergency drugs, supplements and other drugs

• Hydroxyprogesterone Caproate
• Hydroxyzine
• Hypertonic Saline (7.2–7.5% NaCl)
• Imepitoin
• Intravenous Lipid Emulsion (ILE)
• Iron Dextran
• Leflunomide
• Leucovorin (Folinic Acid)

Frequently asked questions