Magnesium supports bone formation, muscle and nerve function, and activates hundreds of enzymes involved in energy metabolism. In cats, magnesium is a nutrient where balance is particularly important — both deficiency and excess can contribute to urinary tract problems. Excess dietary magnesium has historically been linked to struvite crystal formation in alkaline urine, which is why many commercial cat foods carefully control magnesium levels.
A small piece of cooked salmon (about 30g) provides roughly 8–10mg of magnesium — your adult cat needs approximately 12–40mg per day. Commercial cat foods are formulated to provide appropriate magnesium levels without contributing to urinary crystal risk.
0.09% of daily nutrient intake
Magnesium makes up 0.09% of your cat's total daily nutritional requirements by weight. That's a tiny amount — but it matters.
Muscle tremors, weakness, loss of appetite, and poor growth. Severe deficiency can cause cardiac arrhythmias and seizures, though dietary deficiency is rare in cats eating commercial food.
Excess magnesium, combined with alkaline urine and high phosphorus, can promote struvite urinary crystal formation. This is one reason commercial cat foods monitor magnesium levels carefully, typically keeping them below 0.1% on a dry-matter basis.
| Life Stage | Size | Min | Max | Unit | Notes |
|---|---|---|---|---|---|
| Adult | — | 12 | 40 | mg | Magnesium levels are carefully controlled in cat foods to prevent urinary crystal formation. Keep below 0.1% on a dry-matter basis. |
Source: NRC 2006, AAFCO 2024
Magnesium and calcium work together in bone formation and muscle function, but excess magnesium combined with alkaline urine can promote struvite urinary crystal formation in cats.
What this means: Commercial cat foods carefully balance magnesium relative to calcium and control urine pH to prevent crystal formation. If you feed homemade food, keep magnesium levels moderate and ensure adequate water intake to dilute urine.
