Sodium is not a flavour issue for cats, it is a concentration issue. An adult cat needs roughly 100 to 150 mg of sodium a day, a 4 kg cat that takes in 2 g of sodium chloride per kg of body weight in one sitting is at the acute threshold, and a serum sodium above 170 mmol/L is a hospital problem. Between those numbers sits the whole range of ordinary mistakes: a slice of ham, a lap of gravy, a bowl of soup.
Number 1: 0.2 per cent of dry matter is the floor
Complete cat food has to supply about 0.2 per cent sodium on a dry matter basis, which for a 4 kg cat eating 60 g of dry matter works out at roughly 120 mg a day. Most commercial foods sit between 0.3 and 0.6 per cent, so a cat on a normal diet takes in 180 to 360 mg daily with a wide margin above the floor. Below the floor, a cat loses appetite and condition over weeks, not hours; that is a formulation problem, and it is not corrected by adding salt at home.
Number 2: salt is 39 per cent sodium by weight
Table salt is about 39.3 per cent sodium and 60.7 per cent chloride, so 1 g of salt carries 393 mg of sodium and 1 level teaspoon, about 6 g, carries 2.4 g. This conversion is where most home estimates go wrong by a factor of 2.5. A 100 g slice of cooked ham at 1,200 mg sodium is the same as 3 g of salt, and 3 g of salt is 8 to 12 times what a 4 kg cat needs in a day.
Number 3: 2 g per kg is the acute line
Oral sodium chloride becomes a clinical problem around 2 g per kg of body weight, which for a 4 kg cat means about 8 g of salt, and 3 to 4 g per kg, or 12 to 16 g, can be lethal without treatment. The number is not a target to approach: it is the point where the gut starts to draw water, vomiting follows, and serum sodium climbs faster than the brain can adapt. A cat that eats 4 g of salt is at half the acute line and needs a call, not a wait.
Water is the amplifier
The same salt load is far more dangerous in a cat that has no water. A cat without access to water for 24 hours, or one that is already dehydrated from vomiting or a hot room, reaches a higher serum sodium on a smaller dose. Water intake from food matters here: a cat on dry food takes in 5 to 10 per cent of its water with the food, while a wet diet can be 75 to 80 per cent water, which is why the same salty treat lands differently on 2 different bowls.
The symptom clock
Signs move in a predictable order. Vomiting and thirst usually start 30 to 60 minutes after a large salt load. Wobbling, head pressing, and fine tremors appear at 2 to 4 hours. Seizures and stupor belong to the 4 to 12 hour band, and collapse to the 12 to 24 hour band. A cat that only vomited once at 40 minutes and is drinking normally at hour 3 is in a different category from a cat that is wobbly at hour 3.
What 100 g of a food actually carries
| Food, 100 g | Sodium, mg | Salt equivalent, g | Share of a 4 kg cat's daily need |
|---|---|---|---|
| Cooked ham | 1,200 | 3.1 | 8 to 12 times |
| Hard cheese | 700 | 1.8 | 5 to 7 times |
| Commercial soup | 350 | 0.9 | 2 to 3 times |
| Potato crisps | 550 | 1.4 | 4 to 5 times |
| Bread, 1 slice at 30 g | 150 | 0.4 | 1 to 1.5 times |
| Cat treats, 1 stick | 40 | 0.1 | 0.3 times |
Why the brain is the organ at risk
Sodium in the blood pulls water out of brain cells. When serum sodium rises over hours, the brain adapts by generating its own solutes, which takes 24 to 48 hours. A rise that happens in 2 hours gives the brain no time, and the result is swelling inside a closed skull: dullness, then seizures. The same logic makes correction dangerous: a serum sodium lowered faster than 0.5 mmol per L per hour can swell the brain on the way down. This is why a high sodium reading is treated in a clinic with a controlled rate, not with a bowl of water at home.
When it is a clinic visit, today
Any seizure, any tremor, any cat that cannot stand, and any cat with a serum sodium over 170 mmol/L goes in immediately. Vomiting more than twice, refusal of water for 12 hours, or a cat that is dull and pressing its head into a wall are same-day visits. Bring the food wrapper and estimate the amount eaten in grams; the clinic will want the time of ingestion, the estimated sodium load, and whether the cat has passed urine since.
What not to do at home
Do not force large volumes of water by syringe. A cat that has been salt-loaded and is then given water fast can drop its sodium too quickly. Do not give milk to dilute the salt, do not withhold water as a punishment for drinking too much, and do not add salt to food to encourage drinking: that advice belongs to a veterinarian managing a specific condition, not to a general routine. Small sips of fresh water offered freely are the only home step worth taking while you make the call.
5 checks for the next 24 hours
- Weigh the food or the wrapper and write down grams eaten, not a guess.
- Note the hour of ingestion and the hour of the first vomit.
- Offer fresh water in small amounts and count how much is drunk in 2 hours.
- Check gums, gait, and responsiveness at 1, 3, 6, and 12 hours.
- Call a veterinarian or poison line if any tremor, wobble, or second vomit appears.
Two related readings help set the context. Water taken in with food changes how a salt load lands, and the numbers are in water intake from food. Raw diets carry their own contamination questions, covered in raw food and H5N1 risk. If the concern is what a special diet costs per month, the feeding cost calculator does that arithmetic.
Frequently asked
How much salt is actually dangerous for a cat?
Around 2 g of sodium chloride per kg of body weight starts clinical signs, so a 4 kg cat is at the acute line near 8 g of salt, and 12 to 16 g can be lethal without treatment. A single slice of ham is nowhere near that, but 3 or 4 slices plus a bowl of salty soup in one afternoon is a load worth a phone call, especially if the cat has no water.
My cat licked a salted pretzel. Do I need to worry?
Probably not, but do the arithmetic. A 30 g pretzel carries roughly 200 to 300 mg of sodium, which is 2 days of a 4 kg cat's minimum need and still far below the 8 g salt acute line. Offer fresh water, watch for vomiting in the first hour and wobbling in the next 4, and call if the cat vomits twice or seems unsteady rather than merely thirsty.
Why can't I just give water to flush the salt out?
Because the brain adapts to high sodium over 24 to 48 hours, and a fast drop can pull water into brain cells and cause swelling. Home watering should be free access to small amounts, not syringed volumes. A cat with tremors, seizures, or a serum sodium over 170 mmol/L needs a controlled correction rate in a clinic, where sodium can be checked every few hours.