TL;DR
Dog muscle spasms are sudden, involuntary tightening or twitching of a muscle. Many are harmless, like twitching in deep sleep, a brief cramp after hard exercise, or shivering from cold. Others are a warning sign. In a study of 14 dogs with true muscle cramps, 79% had low blood calcium, most often from an underactive parathyroid gland, so a blood test is usually the first step. Spasms can also come from back or neck pain, poisoning (moldy food, compost, some insecticides), seizures and inherited movement disorders in certain breeds. Go to a vet at once if your dog may have eaten something toxic, the spasms affect the whole body, your dog cannot stand or is not responding normally, or an episode lasts more than about 5 minutes.
What muscle spasms look like
Vets separate involuntary movements into a few types, because each points to different causes:
| What you see | What it usually is | Typical causes |
|---|---|---|
| Small flickers or ripples under the skin | Twitches (fasciculations) | Often harmless; also nerve irritation, low calcium |
| A muscle or leg locks hard and painfully for seconds to minutes | Cramp | Low calcium, overexertion, nerve hyperactivity |
| Rhythmic shaking of a leg, head or body | Tremor | Cold, fear, pain, weakness, toxins, idiopathic head tremor |
| Whole-body stiffening and jerking, often with drooling, loss of awareness or wetting | Seizure | Epilepsy, toxins, low blood sugar, brain disease |
| Twitching paws and face during deep sleep, stops when woken | Normal dreaming | No treatment needed |
| Episodes of stiff, odd walking with the dog fully aware | Paroxysmal dyskinesia (episodic movement disorder) | Breed-related conditions such as epileptoid cramping in Border Terriers |
The most useful thing you can do is film an episode on your phone. A short video often tells a vet more than any description.
Common causes of muscle spasms in dogs
1. Low blood calcium
True muscle cramps are uncommon, but when they happen, calcium is the first thing to check. In a 2021 study of 14 dogs with muscle cramps seen by veterinary neurologists:
- 11 of 14 (79%) had low blood calcium: 9 from primary hypoparathyroidism (the glands that control calcium stop working), 1 from intestinal lymphoma and 1 from a protein-losing gut disease.
- In 9 of 14, the cramps were triggered by getting the dog to move.
- 8 of 14 dogs were obviously painful; the others showed only mild discomfort.
Low calcium also causes eclampsia in mothers nursing puppies, which is an emergency: trembling, stiffness, panting and restlessness in the weeks after giving birth.
2. Pain in the back, neck or joints
A painful back or neck often makes the muscles beside the spine go hard and twitch, and a dog with sore hips or knees may tremble when standing. Signs that pain is the cause:
- A hunched back, or reluctance to lower the head to eat or drink
- Crying out when picked up or touched
- Trembling back legs when standing still, which settles when lying down
- Stiffness after rest
See senior dog back legs shaking when standing and arthritis in dogs: treatment and home care.
3. Overexertion, heat and dehydration
After a long run, a hot day or an unusually active weekend, some dogs get brief cramps or trembling in tired muscles, especially dogs that are not used to that much exercise. These settle with rest, water and a cool place. Heat matters: a dog that is trembling, panting hard and weak on a hot day may have heatstroke, which is an emergency.
4. Poisoning
Several common toxins cause tremors and spasms:
- Moldy food, compost and fallen walnuts. Molds such as Penicillium crustosum make tremor-causing toxins (penitrem A). In a report of six poisoned dogs, signs included vomiting, convulsions, tremors, wobbliness and a racing heart; most recovered within days, but two still had neurologic signs four months later.
- Some flea and tick products, especially if a product meant for a larger dog, or for livestock, is used on a small dog.
- Chocolate, caffeine, some human medicines and slug or snail bait.
If your dog might have eaten any of these and starts trembling, go to an emergency vet immediately and take the packaging or a photo.
5. Seizures
A seizure is not a muscle problem but a brain event, and it can look like violent spasms. Clues that it is a seizure: the dog falls over, does not respond to you, paddles its legs, drools, or wets itself, and is confused afterward. A seizure lasting more than 5 minutes, or several in a row, is an emergency.
6. Breed-related movement disorders
Some breeds have inherited conditions that cause episodes of cramping or abnormal movement while the dog stays aware:
- Border Terriers: canine epileptoid cramping syndrome. In a study of 29 affected dogs, most had their first episode before 3 years of age, episodes usually lasted 2 to 30 minutes, and the most common signs were difficulty walking, mild tremor and abnormal muscle tone. About half of the owners who changed the dog's diet saw fewer episodes; later work linked it to gluten sensitivity.
- Scottish Terriers: "Scottie cramp," episodes of stiff, arched walking triggered by excitement or exercise.
- Idiopathic head tremor: episodes of head bobbing in an otherwise normal, alert dog. In a study of 291 dogs, Bulldogs, Labradors, Boxers and Doberman Pinschers made up 69% of cases, the first episode happened before 4 years of age in 88%, and distracting the dog stopped the tremor in 87%. Most dogs did not respond to anti-seizure drugs, and in a UK study, 8 of 10 owners reported that the tremor eased or stopped over time without treatment.
7. Normal twitching in sleep
Twitching paws, flickering eyes, soft barks and running movements during deep sleep are normal dreaming. A dreaming dog wakes up normally when you call its name. A dog having a seizure usually does not respond, and is often confused afterward.
When muscle spasms are an emergency
Go to a vet immediately if:
- Your dog may have eaten a toxin, moldy food, compost or medication
- The spasms involve the whole body, or your dog falls over and does not respond
- An episode lasts more than 5 minutes, or episodes keep coming
- Your dog has recently had puppies and is trembling, stiff or panting
- Spasms come with fever, collapse, vomiting, or very pale or blue gums
- Your dog cannot stand or walk, or cries out in pain
Book a vet visit within a few days if spasms keep coming back, affect one leg, start in an older dog, or come with stiffness, weight loss or changes in appetite.
What the vet will do
- A full physical and neurological exam, including feeling the spine and joints for pain.
- Blood tests, including calcium, blood sugar, electrolytes, kidney and liver values. Given that low calcium caused 79% of the true cramps in the study above, this is a key test.
- Your video of an episode, which helps separate cramps, tremors and seizures.
- X-rays or MRI if back pain or a brain problem is suspected.
- Treatment of the cause: calcium and vitamin D for hypoparathyroidism, pain relief for back or joint pain, decontamination and supportive care for poisoning, or anti-seizure medicine for epilepsy.
How to help a dog with muscle spasms at home
Once your vet has ruled out an emergency:
- Stay calm and keep your dog safe during an episode. Move furniture away and keep your hands away from the mouth.
- Time and film each episode, and keep a log of what happened just before.
- Warmth and gentle massage can ease a cramped or sore muscle, if your dog enjoys being touched there.
- Fresh water and rest after exercise, and no hard exercise in the heat.
- Keep your dog lean and keep it moving gently. Strong muscles support sore joints and a stiff back.
- Do not give human muscle relaxants or painkillers. Many are toxic to dogs.
Muscle spasms in older dogs
In senior dogs, trembling and twitching often go with muscle loss and joint pain: thinner back legs, trembling when standing, and stiffness after rest. Treating the pain and rebuilding muscle with regular, gentle exercise matters most. See muscle atrophy in dogs: causes and how to rebuild muscle and old dog weak back legs.
Diet is part of muscle maintenance too. Our Muscle Strength & Recovery Soft Chews provide 150 mg calcium HMB and 160 mg L-leucine per 2-chew serving, with wild Alaskan salmon oil and green-lipped mussel, as daily support for active and aging dogs. See HMB for dogs: what the research shows for the evidence behind these ingredients.
FAQ
What does a muscle spasm look like in dogs?
Usually a sudden twitch, ripple or hard tightening of a muscle, often in a back leg, along the back or in the face. A cramp can lock a leg stiffly for seconds to minutes. Rhythmic shaking is more often a tremor.
How do you treat muscle spasms in dogs?
Treat the cause. Your vet will usually check blood calcium, sugar and electrolytes, look for back or joint pain and rule out poisoning. Treatment may be calcium supplementation, pain relief, decontamination or anti-seizure medicine. At home, rest, warmth and gentle massage can help a sore muscle.
Did my dog have a seizure or a muscle spasm?
During a seizure a dog usually loses awareness, falls over, paddles, drools or wets itself, and is confused afterward. During a cramp, tremor or twitch the dog usually stays aware and responds to you. A video helps your vet decide.
Why is my dog spasming while sleeping?
Most twitching during sleep is normal dreaming, and the dog wakes normally when called. If your dog stiffens, does not wake when called or is confused after waking, talk to your vet.
Why is my old dog twitching?
In older dogs, twitching and trembling are often linked to joint or back pain, weak muscles or cold. They can also be signs of low calcium, kidney or liver disease or a neurologic problem, so a vet check with blood tests is worthwhile.
Can dehydration cause muscle spasms in dogs?
Heat, hard exercise and dehydration can contribute to cramps and trembling in tired muscles. Offer water, rest your dog in a cool place, and see a vet urgently if your dog is weak, panting heavily or collapsing in the heat.
References
- Gagliardo T, et al. Clinical features of muscle cramp in 14 dogs. Journal of Veterinary Internal Medicine. 2021. PMID: 33247617
- Lowrie M, Garosi L. Classification of involuntary movements in dogs: tremors and twitches. The Veterinary Journal. 2016. PMID: 27387736
- Black V, et al. Phenotypic characterisation of canine epileptoid cramping syndrome in the Border terrier. Journal of Small Animal Practice. 2014. PMID: 24372194
- Lowrie M, et al. The clinical and serological effect of a gluten-free diet in Border terriers with epileptoid cramping syndrome. Journal of Veterinary Internal Medicine. 2015. PMID: 26500168
- Shell LG, et al. Clinical and breed characteristics of idiopathic head tremor syndrome in 291 dogs: a retrospective study. Veterinary Medicine International. 2015. PMID: 26064776
- Liatis T, et al. Idiopathic and structural episodic nonintentional head tremor in dogs: 100 cases (2004-2022). Journal of Veterinary Internal Medicine. 2023. PMID: 37850712
- Eriksen GS, et al. Poisoning of dogs with tremorgenic Penicillium toxins. Medical Mycology. 2010. PMID: 19886763
- Davidson AP. Reproductive causes of hypocalcemia. Topics in Companion Animal Medicine. 2012. PMID: 23415384
- Garosi L, et al. Scottie cramp and canine epileptoid cramping syndrome in Border terriers. Veterinary Record. 2012. PMID: 22354655
For individual health questions, your veterinarian remains the best partner.
