Sudden, shock-like muscle jerks in a dog — called myoclonus — can signal low blood sugar, not just epilepsy, a new study of 10 dogs found. Nine had a pancreatic tumor called insulinoma. If your dog jerks suddenly, especially with weakness or collapse, call your vet promptly and film the episode if safe.
Dog muscle jerks are frightening to watch, and most owners’ first thought is a seizure. A study published October 13, 2026, in the Journal of Veterinary Internal Medicine — reported by Vet Candy on October 24, 2026 — gives owners a new possibility to raise with their vet: dangerously low blood sugar.
What is myoclonus in dogs? Myoclonus is a sequence of brief, shock-like involuntary muscle jerks — sudden contractions or relaxations of one or more muscles. It can affect one area or the whole body. It is different from a rhythmic tremor and from a full seizure, though the three can look similar at first glance.
What did the new study actually find?
Researchers in Belgium and the UK retrospectively studied 10 dogs that developed myoclonus during hypoglycemia. Every dog’s blood glucose was below 3.3 mmol/L (about 59 mg/dL) during the jerking, with a median of 2.07 mmol/L (about 37 mg/dL).
Eight dogs had generalized jerks; two had focal jerks involving the head, and in five the episodes progressed to generalized seizures.
The striking pattern was the underlying cause. Nine of the 10 dogs had suspected, presumptive, or confirmed insulinoma — a tumor of the pancreas’s insulin-producing beta cells that releases too much insulin and drives blood sugar down. The tenth dog developed hypoglycemia as a complication of medical treatment: it had received fast-acting human insulin in hospital for an unrelated condition, and the jerks resolved after the dose was adjusted and glucose given.
Why is low blood sugar so hard to spot?
Insulinoma is tricky to diagnose because blood sugar can swing through the day, and affected dogs can look relatively normal between episodes — in this study, neurological exams were completely normal in five of the 10 dogs between episodes.
Other signs of low blood sugar include weakness, tremors, behavior changes, unsteadiness, collapse, and seizures. Because episodes are intermittent, the researchers relied heavily on owner-supplied video — a phone video may be one of the most useful things you bring to the appointment.
How can I tell jerks from a seizure or a tremor?
These movements overlap — only a vet can sort them out — but these distinctions help you describe what you saw:
- Myoclonus: brief, shock-like jerks, irregular, in one area or the whole body.
- Tremor: more rhythmic, repetitive shaking, like shivering that will not stop.
- Seizure: often stiffening, paddling, drooling, and loss of awareness, usually longer than a single jerk.
- Fasciculations: small, localized twitches under the skin, without larger jerking movements.
Do not try to diagnose at home. Note the time, how long the episode lasted, what your dog was doing just before, whether they stayed aware, and anything they may have eaten or any medication given recently. Toxins can also cause tremors and jerks, so if your dog may have eaten something unusual, our free Dog-Ate-Something Toxin Checker can help you work out how urgent it is.
What should I do if my dog starts jerking suddenly?
- Stay calm and keep your dog safe. Move hazards away, keep hands clear of their mouth, and do not try to hold them still.
- Film it if you can. A short video helps your vet enormously, since episodes often stop before the appointment.
- Call your vet promptly — urgently if jerks repeat, or come with collapse, seizures, or unresponsiveness. Mention any weakness, behavior changes, missed meals, and insulin or diabetes medication if relevant.
- Do not give food, sugar, or home remedies unless your vet tells you to. A jerking or disoriented dog can choke, and the wrong treatment can make things worse.
- Write down the details. Time, duration, triggers, and what happened afterward — this history shapes the diagnosis.
At the clinic, measuring blood glucose during or soon after an episode is a quick, important step, the researchers emphasize. A low reading can point to a reversible metabolic cause rather than a primary brain disorder. If insulinoma is suspected, your vet may discuss testing and options such as medication, dietary management, or surgery. In the study, treated dogs improved short term, though benefits did not always last — four dogs were eventually euthanized because of recurrent hypoglycemia and jerks, which is why early investigation matters.
What are the limits of this study?
Honesty matters here. This was a small, retrospective study of just 10 dogs, mostly with insulinoma, with differences in testing, treatment, and follow-up. The researchers could not consistently measure how often or how long individual jerks lasted, and without EEG recordings they could not definitively say whether every episode was epileptic or non-epileptic. The findings do not mean every jerking dog has low blood sugar — they mean low blood sugar deserves a place on the checklist, especially when jerks recur or come with weakness, collapse, or behavior changes.
FAQ
What causes sudden muscle jerks in dogs?
Several things, including epilepsy, toxins, medications, metabolic problems, and structural brain disease. A new 2026 study adds low blood sugar: 10 dogs developed myoclonus during hypoglycemia, and nine had suspected or confirmed insulinoma. Your vet can narrow the cause with an exam, blood glucose measurement, and history.
Is myoclonus in dogs the same as a seizure?
Not exactly. Myoclonus means brief, shock-like jerks; seizures often involve stiffening, paddling, drooling, and loss of awareness. The two can occur together — in the study, five dogs’ episodes progressed to generalized seizures — so any jerking episode deserves a vet visit rather than a home diagnosis.
What is insulinoma in dogs?
Insulinoma is a tumor of the pancreas’s insulin-producing beta cells. It releases excess insulin, driving blood sugar down and causing weakness, collapse, behavior changes, seizures, and — per this study — sudden muscle jerks. It can be hard to diagnose because glucose levels fluctuate and dogs may seem normal between episodes.
Should I give my dog sugar if it starts jerking?
Do not give food, sugar, or home remedies unless your vet instructs you to. A jerking or disoriented dog can choke, and the cause may not be low blood sugar at all. Call your vet promptly, film the episode if safe, and follow their guidance.
When is a jerking episode an emergency?
Seek urgent care if jerks repeat, last a long time, come with collapse, seizures, or unresponsiveness, or if your diabetic dog received insulin but skipped a meal. Bring your video, medication list, and notes about timing and triggers.
🐾 Keep your dog’s health checks in one place
Bookmark our free Dog-Ate-Something Toxin Checker for fast guidance when your dog eats something unexpected, and try the free Dog Wellness Planner for a personalized care plan. The Pro Pet Pass ($7/month) unlocks our full Pro toolset.
Sources: Polidoro et al., Journal of Veterinary Internal Medicine, October 13, 2026; Vet Candy news report, October 24, 2026; ScienMag summary. Informational only — not veterinary advice; consult your vet about any sudden movement changes in your dog.