Insulin Therapy for Pets: A Complete Guide to Home Injections

Not all insulins are the same, and the type your vet prescribes will depend on whether you have a dog or a cat, as well as your pet's individual response to treatment. Understanding the different options helps you feel confident about your pet's medication.

"The most common mistake I see is owners assuming all insulin works the same way. The type, timing, and handling all matter — and getting the basics right from the start makes a world of difference for your pet's glucose control." — Dr. Sarah Chen, DVM

For Dogs

• Caninsulin / Vetsulin: This is the most widely prescribed insulin for dogs worldwide. It is a porcine-derived (pig) intermediate-acting insulin (lente type) that closely matches canine insulin. It is typically given twice daily and has a duration of action of around 10-14 hours.
• NPH (Neutral Protamine Hagedorn) insulin: A human recombinant intermediate-acting insulin that is also commonly used in dogs. It has a similar duration to Caninsulin and is widely available at pharmacies, which can make it more convenient and sometimes more affordable.

For Cats

• ProZinc (protamine zinc insulin): Specifically formulated for cats and widely recommended. It provides a smooth, sustained insulin release that suits feline metabolism well.
• Glargine (Lantus): A long-acting human insulin analogue that has become increasingly popular for cats due to its flat, peakless action profile. Studies have shown particularly high remission rates when glargine is started early alongside a low-carbohydrate diet.

Your vet will select the best option based on your pet's needs and may adjust the type if the initial choice does not provide adequate control. For a broader overview of diabetic care, see our diabetes management guide for pets.

Insulin is a fragile protein that can be rendered ineffective by improper storage and handling. Following these guidelines carefully ensures your pet receives the full benefit of every dose.

Storage

• Refrigerate at all times: Unopened and opened insulin vials should be stored in the refrigerator at 2-8°C (36-46°F). Place the vial in the door shelf or a designated spot where it will not be pushed to the back and accidentally frozen.
• Never freeze insulin: Freezing destroys insulin's molecular structure and renders it useless. If your insulin has been frozen — even once — discard it.
• Avoid heat and direct sunlight: Do not leave insulin on a windowsill, in a car, or near any heat source. Exposure to temperatures above 30°C (86°F) degrades insulin rapidly.
• Check expiry dates: Unopened insulin is good until the manufacturer's expiry date when stored correctly. Once opened, most insulin vials should be used within 28-42 days (depending on the brand) — mark the opening date on the vial with a marker.

Handling Before Injection

• Gentle mixing: Some insulins (like Caninsulin and NPH) are suspensions and need to be mixed before each use. Roll the vial gently between your palms 10-20 times — never shake it vigorously, as shaking creates air bubbles and can damage the insulin molecules. The insulin should appear uniformly milky after mixing.
• Clear insulins (glargine, ProZinc): These are solutions and should appear clear and colourless. If they appear cloudy, discoloured, or contain particles, discard the vial.
• Allow to reach room temperature: Drawing up cold insulin and injecting immediately can cause mild stinging. Letting the vial sit at room temperature for 5-10 minutes before use can improve comfort. However, do not leave it out of the fridge for extended periods.

Giving your pet an insulin injection at home may seem daunting at first, but most owners become comfortable within just a few days. The needles used are extremely fine — your pet will often not even notice the injection.

What You'll Need

• Insulin vial (correctly stored and mixed if needed)
• Insulin syringes matched to your insulin concentration (U-40 syringes for Caninsulin/Vetsulin, U-100 syringes for ProZinc/glargine/NPH — never mix up syringe types)
• A treat or meal to reward your pet (and to coincide with the injection)

Drawing Up the Dose

1. Wash your hands and gather your supplies.
2. Gently roll the vial (if it's a suspension) until uniformly milky.
3. Insert the needle through the rubber stopper and draw up slightly more insulin than prescribed.
4. Hold the syringe needle-up and flick gently to move any air bubbles to the top, then push the plunger to expel the air and return to the exact dose.

Giving the Injection

1. Position your pet: Have your pet eating a meal or being gently held. Many owners find that giving the injection while the pet eats is the easiest approach — the pet is distracted and associates the injection with something positive.
2. Tent the skin: Using your non-dominant hand, gently pinch and lift a fold of skin along the scruff of the neck or the loose skin along the side of the body (flank).
3. Insert the needle: With the bevel (angled opening) facing up, insert the needle smoothly into the base of the skin fold at approximately a 45-degree angle. The needle should slide easily under the skin into the subcutaneous space.
4. Inject the insulin: Push the plunger steadily and completely. Hold for 1-2 seconds, then withdraw the needle smoothly.
5. Rotate injection sites: Alternate between different areas each day — left side, right side, different spots along the scruff and flanks. This prevents lipodystrophy (lumps or thickening of the skin) that can impair insulin absorption.

Dispose of used syringes in a sharps container — never reuse needles.

Consistency is the single most important factor in successful insulin therapy. A predictable daily routine keeps blood glucose levels as stable as possible and reduces the risk of dangerous highs or lows.

Timing Is Everything

Administer insulin at the same times each day, approximately 12 hours apart. Most owners find that aligning injections with their own daily anchors — such as morning breakfast and evening dinner — works best. For example, 7:00 AM and 7:00 PM. A variation of 30-60 minutes is generally acceptable, but try to stay as close to the schedule as possible.

Always Pair Insulin With a Meal

Your pet should eat immediately before or alongside each insulin injection. This ensures that glucose from the meal enters the bloodstream as the insulin begins working. If your pet refuses food, do not give the full insulin dose — contact your vet for guidance, as injecting insulin without a meal can cause dangerous hypoglycaemia.

What to Do If You Miss a Dose

Life happens, and occasionally you may miss or be late with an insulin dose. The golden rule is: never double up. If you miss a dose entirely, simply give the next scheduled dose at its normal time. If you realise the dose is only a couple of hours late, give it and adjust the next dose timing slightly to maintain the 12-hour spacing. When in doubt, contact your vet.

Keeping Records

Maintain a simple log of each injection — date, time, dose given, whether your pet ate, and any observations (energy level, water intake, urination). This record is invaluable for your vet when making dose adjustments. Many owners use a spreadsheet or a notes app on their phone for convenience.

For broader guidance on maintaining your pet's health through regular veterinary check-ups, visit our vet visit frequency guide.

Even the most dedicated pet owners can make mistakes with insulin therapy — especially in the early days. Being aware of common pitfalls can help you avoid them from the start.

Top Mistakes

• Using the wrong syringe type: U-40 insulin requires U-40 syringes; U-100 insulin requires U-100 syringes. Using the wrong syringe will deliver the wrong dose — potentially a dangerous overdose or underdose. Always double-check the syringe matches your insulin.
• Shaking the insulin vial: Vigorous shaking creates bubbles, makes accurate dosing difficult, and may denature the insulin protein. Always roll gently.
• Injecting into muscle: Insulin should go under the skin (subcutaneously), not into muscle. If you are lifting the skin fold properly and inserting at the correct angle, this should not happen. Muscular injection causes faster, unpredictable absorption.
• Inconsistent feeding: Changing food types, amounts, or feeding times disrupts glucose control. Stick to the same diet and schedule every day.
• Adjusting the dose without vet guidance: Changing the insulin dose on your own — even with good intentions — can cause serious problems. Always consult your vet before any adjustments.
• Not rotating injection sites: Injecting in the same spot repeatedly causes tissue damage and erratic insulin absorption. Rotate systematically.

If you ever have concerns about your injection technique or your pet's response to insulin, our pet first aid essentials guide covers how to handle common emergencies, including hypoglycaemia.

Travel requires extra planning when your pet is on insulin therapy, but with preparation it is entirely manageable — whether you're heading to the countryside for a weekend or flying overseas.

Packing Essentials

• Insulin and syringes: Bring more than enough for the trip plus extra in case of delays. Carry insulin in a small insulated cool bag with an ice pack to maintain the correct temperature.
• Glucometer and test strips: If you monitor at home, pack your full testing kit.
• Food: Bring your pet's regular food — enough for the entire trip plus a buffer. Changing food while travelling adds an unwelcome variable.
• Sharps container: For safe syringe disposal.
• Vet records and medications list: In case you need to visit a local vet at your destination.

During the Journey

Try to maintain your pet's normal injection and feeding schedule as closely as possible. If crossing time zones, consult your vet in advance about how to shift the schedule gradually. On car journeys, keep insulin in a cool bag — never in the boot or on the dashboard where temperatures can spike. On flights, carry insulin and supplies in your hand luggage (insulin should never go in checked luggage due to freezing risk in the cargo hold).

At Your Destination

Immediately store insulin in a fridge upon arrival. Identify the nearest emergency veterinary clinic before you need one — a quick search before you leave home gives you peace of mind. Keep your pet's routine as close to normal as possible: same meal times, same walks, same injection schedule.

With a little forward planning, diabetes should not stop you and your pet from enjoying time away together. The key is preparation and consistency.