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My diabetic dog chewed and swallowed about half the liquid from a used insulin pen — is the plastic casing or remaining insulin dangerous?

Dogs · Emergency guide

Last reviewed: 2026-09-05 · Reference ranges: ASPCA, Pet Poison Helpline & Merck Veterinary Manual

Short answer

Yes, this is an urgent situation. The insulin itself is the primary danger, as it will rapidly lower your dog's blood sugar, potentially leading to weakness, tremors, seizures, or collapse within 30 minutes to a few hours. The plastic casing poses a secondary risk of causing a gut blockage or injury. Do not wait for signs to appear. If your dog is awake and able to swallow, offer a small amount of honey or syrup and go to the vet immediately, bringing the pen with you so they can estimate the dose ingested.

Why is this dangerous?

Insulin injected or chewed from a pen, and oral drugs such as metformin and glipizide, all lower blood glucose. A pet that has taken too much becomes hypoglycaemic — the brain runs out of fuel within 30 minutes to a few hours.

Pets already on insulin are at extra risk: a double dose or a chewed insulin pen is a common household accident.

Why speed matters

Delaying care significantly worsens outcomes. Some signs appear hours or days later, so "looks fine right now" is not a reason to wait.

Signs to watch for

  • Weakness, wobbliness, staggering
  • Confusion, staring, unusual behaviour
  • Tremors, seizures
  • Collapse, coma
  • Vomiting and drooling before neurological signs

What to do right now

  1. If the pet is awake and able to swallow, offer a small amount of honey, syrup or food and call the vet at once.
  2. Do not put anything in the mouth of a drowsy or seizing pet — it can be inhaled.
  3. Go to the vet; blood glucose needs to be measured and monitored for hours.
  4. Bring the pen or bottle so the dose taken can be estimated.
If your pet shows any of the signs above, go to the nearest emergency vet now and call ahead.

The step-by-step response, from the first minute to the vet visit, is in our Diabetes Medicines (Metformin, Insulin) emergency guide.

Open the full emergency guide: Diabetes Medicines (Metformin, Insulin) →