Missed or uncertain insulin dose in dogs and cats: what to do
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Missed your pet's insulin, or unsure whether the full dose went in? What to do next, what not to do, and exactly what your vet will need to know.
Quick answer
Note the time, and ask your vet about the next dose rather than deciding yourself. Do not give a second dose to make up for a missed one.
A missed or uncertain dose should not, in itself, become an emergency. Too much insulin is the version that can be, which is why doubling up is the mistake vets most want to avoid.
If your pet shows weakness, wobbliness, trembling, disorientation or collapse after a possible double dose, treat it as an emergency and contact a vet immediately.
Why doubling up is the real danger
A missed or incomplete dose can leave blood glucose higher than planned. Giving another dose when some insulin may already have been absorbed can instead drive blood sugar dangerously low. This is why the safest general rule is not to guess or double-dose.
Common scenarios
- A fur shot: the insulin landed on the coat or you found wet fur after the injection.
- Your pet moved mid-injection: you are unsure how much went in.
- A forgotten dose: you noticed after the planned time.
- An uncertain dose: you cannot remember whether the injection happened.
In each situation, write down what you know and ask your vet if the circumstances are unclear.
What to write down before you phone your vet
Note the time, what you think happened, whether your pet has eaten, any food or insulin you can account for, and how your pet seems now. Include recent exercise, vomiting or diarrhoea if relevant. These details help your vet give advice based on the actual situation.
What not to do
Write down what happened and when, then ask your vet what to do about the next dose. Doubling up is the mistake vets most want to avoid, and a single glucose reading is not enough to decide a change of treatment on.
When it becomes urgent
A missed or uncertain dose should not, in itself, become an emergency. That is worth knowing at 2am: the situation you are in is one to raise with your vet, not usually one to panic about.
Too much insulin is the version that can become urgent. If a dose was doubled, or you cannot rule that out, watch for weakness, wobbliness, trembling, disorientation, unusual sleepiness, collapse or seizures. These can be signs of hypoglycaemia.
If low blood sugar is possible
If your pet is awake and can eat easily, offer them a meal. If they will not or cannot, vets generally advise rubbing honey or glucose syrup on the gums — roughly a quarter to half a teaspoon for a small dog or cat, up to a tablespoon for a large pet — while you arrange transport. It is a bridge to emergency care, not a treatment to repeat at home. If your pet is unconscious or having a seizure, do not put anything in their mouth — take them to the vet straight away.
See the hypoglycaemia guide for the full version.
Read the full hypoglycaemia guide, and use the diabetic pet emergencies guide if your pet is seriously unwell. For newly diagnosed owners, the Just Diagnosed guide explains how to build a safe routine.
Sources
The pages below were each opened and checked before being listed here, and anything that could not be opened was left off rather than guessed at.
- Caninsulin 40 IU/ml: package leaflet (Vm 06376/4083) — Veterinary Medicines Directorate, Defra, revised February 2026. The rule this whole page rests on, from the UK regulator's own leaflet: if only part of a dose went in, do not re-dose — give the usual dose at the next injection.
- Caninsulin 40 IU/ml Suspension for Injection — MSD Animal Health UK, prepared October 2024. The same instruction for a partial VetPen dose: wait, and give the usual dose next time.
- ISFM Consensus Guidelines on the Practical Management of Diabetes Mellitus in Cats — Journal of Feline Medicine and Surgery 17(3):235–250, 2015. That a missed injection is an acceptable compromise rather than an emergency, and that owners should not make dose decisions without their vet.
- 2018 AAHA Diabetes Management Guidelines for Dogs and Cats — Journal of the American Animal Hospital Association 54(1):1–21, 2018. The asymmetry: owners may skip or reduce a dose on suspicion of a hypo, but adding one is never theirs to decide.
When to contact your vet
- Contact your vet promptly if your pet’s symptoms, appetite, drinking, urination, behaviour or glucose readings change unexpectedly.
- Ask your vet for advice before changing insulin, food, exercise or any other part of your pet’s routine.
- Seek urgent veterinary care for collapse, seizures, severe weakness, repeated vomiting, or suspected hypoglycaemia or diabetic ketoacidosis.
Quick answers
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