Magnesium Sulfate

Yes. Too much magnesium in the food can raise the risk of struvite urinary stones, especially in cats whose urine is alkaline.

Magnesium sulfate is a magnesium salt, the same compound as Epsom salt, used in small amounts as a mineral source. Cats need magnesium, and the Merck Veterinary Manual notes that excess magnesium is excreted in the urine. For a cat with a history of urinary crystals or stones, your veterinarian can advise on magnesium intake.

Source: merckvetmanual.com

Magnesium sulfate is added to supply magnesium. It dissolves easily in water, which can help in wet recipes. It is rare in dry cat foods, and appears on only two of the foods we track. The amount is small, so it sits near the end of the ingredient list.

Yes, Epsom salt is magnesium sulfate. Bath products and garden Epsom salt are not made for feeding, and you should not give them to a cat. In cat food, a purified feed-grade version is used in small, measured amounts. Keep household Epsom salt out of a cat's reach.

Some cat food labels list magnesium in the guaranteed analysis, often as a maximum percentage. Magnesium comes mainly from meat and bone, with added sources like magnesium sulfate used in only a few recipes. When a label does not show it, the manufacturer can usually provide the figure.

Pettings gives magnesium sulfate 3 out of 5 and lists it as a mineral. It appears on 2 of the 149 dry cat foods we list. Our How We Score page explains how ingredient scores are set. Each food's page shows how it scores overall.