Insulin injections and your diabetic dog

Don’t worry — with a little guidance and routine, it quickly becomes part of your daily care routine like brushing your teeth every morning. 

Our first lesson on giving injections was late at night and left us confused and processing too much detailed information, so we put together this overview to help others and explain what you need to know about insulin, syringes, and giving injections safely and confidently.

Injections are the third step in the test-feed-inject routine

These instructions apply if all of the following are true:

• You just tested your dog’s blood glucose and the number does not indicate hypoglycemia (below 8.3 mmol/L in Canada or 150 mg/dL in the USA)
• Your dog has eaten their entire meal
• Their previous injection was 11 - 13 hours ago

If your dog’s blood glucose reading is unusually low or if they refuse their meal, skip the insulin and contact your veterinarian before giving the next dose.

When to give injections

Insulin is usually given right after your dog finishes their meal, once you know they’ve eaten their full portion.

Important: Your insulin and syringe types must match

One of the most important things to know is that insulin and syringes are not all the same. Insulin for dogs comes in different strengths, which are measured in “units” (U). The two common types are:

• U-40 insulin (40 units per millilitre)
• U-100 insulin (100 units per millilitre)

Each type requires a matching syringe:

• Use U-40 syringes for U-40 insulin
• Use U-100 syringes for U-100 insulin

Using the wrong syringe type can result in giving too much or too little insulin, which can cause serious blood sugar swings. 

When Parker was first diagnosed diabetic he was prescribed Vetsulin, but we switched to Humulin N about six months afterwards, which required different needles. So we had to dispose of the Vetsulin needles to avoid the risk of someone – such as a dogsitter – using them.

Always double-check the label on your insulin vial and syringe before every injection.

Prepare the insulin vial

1. Wash your hands before handling the vial. Dry them carefully. We have a silicone sleeve on our vial which makes it easier to handle and more shatterproof.
2. Follow the manufacturer's instructions and either gently roll the vial between your palms or shake it.
3. Clean the rubber top of the vial with a fresh alcohol wipe before inserting the needle. This keeps bacteria out of the vial and prevents contamination.

If you’re using insulin pens, follow your veterinarian’s instructions for attaching a new needle and priming before each dose.

Measure the dosage

Your veterinarian will tell you the exact dose your dog needs — for example, “6.0 units twice a day.”

Here’s what to do:

1. Remove the syringe cap (or caps) and set aside. I use the cap as a rest for the syringe when it’s ready to keep the needle away from surfaces.
2. Pull back the plunger to draw in air equal to your dog’s insulin dose. This step helps prevent a vacuum from forming inside the vial, making it easier to draw the correct amount.
3. Insert the needle into the insulin vial through the rubber top. If you miss and the point touches something other than the rubber seal, discard the needle and start over. Needles are inexpensive and it’s not worth the risk of contamination or a bent needle tip.
4. Inject all the air into the vial to equalize pressure.
5. With the needle still in the vial, turn it upside down and slowly draw insulin into the syringe to the correct unit mark. I find it easier and safer to go beyond the desired amount and then use the needle’s plunger to push the extra insulin back into the vial.
6. Check for air bubbles — if you see any, tap the syringe gently to move them to the top, then push them out and re-measure the dose. If you’re unsure, start over.

Give the injection

Most diabetic dogs receive their insulin just under the skin (subcutaneous injection). Your vet or a technician will show you the best spot — often along your dog’s side or below the scruff area, where there’s a loose fold of skin. 

1. Hold a small fold of skin between your thumb and fingers to create a tent of skin.
2. Insert the needle at a slight angle (about 45°) into the fold.
3. Push the plunger smoothly to inject the insulin.
4. Remove the needle and praise your dog — a calm word or treat goes a long way!

The dreaded fur shot

If you smell insulin – it has a strong medicinal scent – or notice a wet spot on your dog’s fur, you may have given what’s called a ‘fur shot.’

It happens to everyone, especially if your dog has long or thick fur, or moves unexpectedly during the injection. Parker is a Terrier and despite his advanced age can still move quickly.

Do not give them another injection. You don’t know how much insulin they received and it’s riskier – possibly life-threatening – to give too much insulin than too little. 

Discard the needle and store your insulin

Keep insulin refrigerated, but not frozen. Avoid storing it in the fridge door, where temperatures fluctuate most. We use a plastic bento box which doesn’t get lost in our packed fridge and has a small compartment perfect for the vial.

Store syringes and supplies out of children’s reach.

Dispose of used syringes in a sealed sharps container or as directed by your local pharmacy or vet clinic. In Canada, many pharmacies like Shoppers Drug Mart provide sharps containers for free and accept full ones for safe disposal.

Talk to your vet

If anything looks unusual like redness at the injection site, loss of appetite, or unexpected blood sugar changes, let your vet know right away.

Your veterinarian is your best partner in managing insulin therapy. Ask them to watch you give an injection, confirm your technique, and check your supplies.

We hope this gives you a shot of confidence

You’ve got this. Know that giving insulin is not just an act of life, it’s an act of love and care that keeps your diabetic dog healthy and happy every day.

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