Cat Trembling or Shaking: 5 Causes Ranked

Shaking in a cat is a symptom with 5 common roots: cold, pain, nerve disease, low blood sugar, and poison. The fastest way to narrow it is to take a temperature and a blood glucose reading before you do anything else. A cat under 37.5 C (99.5 F) or under 60 mg/dL is a medical case, not a behavior problem. A cat that is conscious, responsive, and shivering in a 18 C room is usually just cold.

First: is it shivering, tremor, or a seizure?

The three look similar at a glance and are handled very differently. Shivering is whole-body, fast, and stops when the cat warms up or settles. A tremor is rhythmic and continues during rest, often in one limb or the head, and does not stop with warming. A seizure involves loss of awareness, jaw chattering, paddling, salivation, and 30 to 120 seconds of unresponsiveness, followed by 5 to 30 minutes of confusion. Video 20 to 30 seconds on your phone: a recording changes the diagnosis more often than a description does.

Cause 1: cold, and how to warm safely

A cat below 37.5 C is hypothermic, and below 35 C the shiver reflex itself fails, so a very cold cat may stop shaking and go quiet — a worse sign, not a better one. Warm in 3 steps. First move the cat to a 22 to 25 C room and dry any wet fur. Second wrap the body in a blanket and add a 37 to 39 C heat source against the flank, never the whole body, and never a hot water bottle straight from the kettle. Third recheck the temperature every 10 to 15 minutes. Warm no faster than 1 C per hour; rapid rewarming drops blood pressure. Below 36 C, or any cat that cannot stand, goes to the clinic rather than the blanket.

Cause 2: pain, the most missed one

Cats shiver with abdominal pain, back pain, a blocked bladder, or a fractured tooth, and they do it quietly. Look for a hunched back, squinted eyes, ears turned out, a 12 hour refusal to jump, or a hard 4 cm bladder in a male cat that has produced no urine for 8 hours. A blocked tom is a same-day emergency: 24 to 48 hours of obstruction can push potassium above 7 mmol/L and stop the heart. Never give 1 dose of ibuprofen or paracetamol for the shaking; both are toxic at 1 tablet for a 4 kg cat.

Cause 3: nerve and brain disease

Head tremors, a head tilt, nystagmus, or weakness that worsens over 2 to 6 weeks point to cerebellar or vestibular disease, toxoplasmosis, FIP, or thiamine deficiency. A fine head tremor in an older cat that appears only when concentrating can be a benign intention tremor, but it still deserves 1 exam. Anything with a 24 hour onset, circling to 1 side, or a pupil that stays dilated needs imaging, not observation.

Cause 4: low blood sugar under 60 mg/dL

Normal feline glucose runs 70 to 150 mg/dL. Under 60 mg/dL you see trembling, then wobbly walking, then 1 to 2 minutes of seizure, then coma. Causes include an insulin overdose in a diabetic cat, a liver shunt in a kitten, sepsis, and 24 hours of not eating in a small cat. If the cat is conscious enough to swallow, rub 1 to 2 mL of honey or 50 percent glucose gel on the gums and recheck in 5 to 10 minutes. If it cannot swallow, do not put anything in the mouth; that is how aspiration pneumonia starts. Hypoglycemia in diabetic cats has the insulin dose math.

Cause 5: poison, with a 30 minute clock

Permethrin from a dog flea product causes fine muscle tremors within 30 minutes to 4 hours in cats; 1 drop of a 45 percent spot-on is enough. Other triggers: lily pollen, organophosphates, metaldehyde slug bait, chocolate above 20 mg/kg theobromine, and zinc from pennies. Tremors plus drooling plus dilated pupils after any exposure is a poisoning until proven otherwise, and decontamination is only useful in the first 1 to 2 hours. Check the product against the toxicity lookup before washing or waiting.

Differentiation table

Pattern	Temperature	Glucose	Duration	Awareness
Shivering (cold)	Under 37.5 C	60-150 mg/dL	Stops on warming	Normal
Pain tremor	37.5-39.2 C	60-150 mg/dL	Hours, waxing	Normal
Intention tremor	37.5-39.2 C	60-150 mg/dL	Seconds, on movement	Normal
Hypoglycemia	Often under 37 C	Under 60 mg/dL	1-2 min episodes	Reduced
Seizure	Normal or 40 C+	Variable	30-120 sec	Lost
Permethrin toxicity	Normal or 39.5 C+	60-150 mg/dL	6-72 h	Normal but agitated

Send-to-hospital thresholds

• Temperature below 36 C, or a cat that cannot stand after 15 minutes of warming.
• Glucose below 60 mg/dL that does not rise 10 minutes after oral glucose.
• Any seizure lasting over 2 minutes, or 2 seizures inside 24 hours.
• Tremors within 4 hours of a flea product, a lily, or slug bait.
• Male cat, no urine for 8 hours, hard bladder on palpation.
• Labored breathing over 40 breaths per minute at rest, or blue gums.

A cat that seizes for more than 5 minutes, or has 3 seizures in 24 hours, is in status epilepticus; the seizure protocol covers the 3 minute rule and what to do with the body during one. Whatever you find, write it down: time, temperature, glucose, duration, and what the cat ate in the previous 12 hours. Three data points turn a vague story into a diagnosis.

What to do in the next 10 minutes

Take the temperature, take the glucose if you have a meter calibrated for cats, and video 20 seconds of the episode. Warm only to 37.5 C, no faster. Remove any flea product with warm water and dish soap if the exposure was in the last 2 hours, and call the clinic with the product name, the concentration, and the volume applied. Do not force food or water into a shaking cat. If the cat is a diabetic on insulin, skip the next dose until glucose is above 100 mg/dL and the vet has been called.

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