Low-Carb Cat Food: What 'Dry Matter Basis' Actually Means

If you spend any time in feline diabetes communities, you’ll see the phrase “dry matter basis” (or DMB) constantly. It sounds technical, but the idea is simple, and once it clicks you’ll never read a pet food label the same way.

The problem: water hides everything

Canned cat food is typically 75–82% water. Dry kibble is around 6–10% water. That means the percentages printed on the two labels describe completely different things.

Imagine two foods:

• Canned food A: 10% protein on the label
• Dry food B: 35% protein on the label

Food B looks three times more protein-rich. But strip out the water and food A, with 10% protein in only 22% total “dry matter”, is actually about 45% protein on a dry matter basis. It’s the more protein-dense food by far.

The same distortion applies to carbohydrates, which is what most of us caring for a cat with diabetes care about most.

How to convert any number to dry matter basis

Nutrient (DMB) = nutrient % as fed ÷ (100 − moisture %) × 100

That’s it. Divide by the non-water fraction.

A canned food with 4% carbs as fed and 78% moisture: 4 ÷ 22 × 100 = 18% carbs DMB. A “low” number on the label turns out to be a fairly high-carb food.

(Not sure how to get the carb number in the first place? Carbs aren’t printed on labels. See our guide on how to calculate carbs in cat food, or use the free carb calculator which does both steps for you.)

What counts as “low-carb” for a cat with diabetes?

Here’s a distinction that trips up almost everyone, including a lot of well-meaning advice online. The veterinary consensus guidelines (ISFM, AAHA) put the low-carb target at carbohydrates under about 12% of calories (metabolizable energy), roughly 3 grams per 100 kcal. The widely repeated “under 10%” number also refers to percent of calories, not dry matter.

So why does this article talk about dry matter basis? Because percent-of-calories needs the food’s calorie content, which often isn’t on the label, while dry matter basis can be worked out from the guaranteed analysis alone. The two are related but not the same number. For most foods, especially the higher-fat, low-carb canned options, the dry matter carb figure runs a little higher than the percent-of-calories figure, so a result under about 10% on a dry matter basis generally sits comfortably within the calorie-based target. It’s a practical screening proxy, not a substitute for the calorie calculation.

Roughly speaking: some foods made for cats with diabetes come in well under 10% DMB; many ordinary canned foods land between 10% and 25%; most dry foods sit between 25% and 40% because kibble physically needs starch to hold its shape.

Three important caveats:

1. This is general guidance, not a prescription. Your veterinarian knows your cat’s full picture (weight, kidney values, concurrent conditions) and should confirm any diet change.
2. Never change food abruptly in an insulin-treated cat without veterinary guidance. A sudden drop in dietary carbs can change insulin needs significantly.
3. Labels are minimums and maximums, not exact values. The math gives you a good estimate, not a lab analysis. For exact numbers, manufacturers will usually provide a “typical nutrient analysis” on request.

The fast way to compare foods at the store

Standing in the pet food aisle doing long division is nobody’s idea of fun. Two shortcuts:

• Use our free cat food carb calculator. It computes carbs DMB from any label in seconds, on your phone.
• Or use the Pawpoy app: an AI scanner that reads the label from a single photo, runs this exact math, and tells you how the food fits your cat specifically. It’s free in early access; join the waitlist and we’ll email you when your spot opens.

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Pawpoy is a decision-support and tracking tool, not veterinary advice. Always confirm food changes with your veterinarian, especially for cats on insulin.