The supplements a homemade dog diet needs, and the ones it does not

Published 2 October 2026. Not yet reviewed by a board certified veterinary nutritionist. Numbers marked as engine output come from the Petcare engine on the date shown.

Petcare's recipe for a healthy 20 kg adult dog needs three additions: 2.2 g of calcium a day as 5.4 g of calcium carbonate, 0.6 g of salt for chloride, and 280 mcg of iodine from a vitamin and mineral product. Fish oil is optional. Glucosamine, probiotics, turmeric, coconut oil and vinegar add nothing a healthy dog needs.

What food covered, and what it could not

The dog behind these numbers is a 20 kg neutered female, five years old, walked daily, on a low budget. Petcare sets her energy at 1,059 kcal a day and builds a 728 g recipe of 1,091 kcal: egg 254 g, oat bran 126 g, broccoli 109 g, peas 73 g, beef shank 65 g, lamb heart 44 g, lamb liver 44 g and sunflower seed 13 g. The recipe is checked against 40 nutrient standards, each minimum the higher of the NRC 2006 allowance and the FEDIAF 2025 minimum, scaled to her metabolic weight Grade A. Food met 37 of the 40.

Chloride and iodine read zero because the USDA based ingredient table holds no values for them, so the engine doses both rather than guess. Real food carries some iodine, but not reliably enough to skip it.

Calcium: the gap that defines homemade feeding

Egg, muscle meat and organ meat carry a lot of phosphorus and almost no calcium, because the calcium in an animal sits in its bones, and a cooked recipe leaves the bones out. This recipe holds 2,072 mg of phosphorus against 321 mg of calcium, a calcium to phosphorus ratio of 0.16. Adult dogs need the ratio between 1:1 and 2:1 (FEDIAF 2025 and AAFCO) Grade A. Petcare therefore adds 2,165 mg of calcium a day, which is 5.4 g of calcium carbonate, lifting the ratio to about 1.2. That is twice the 1,003 mg shortfall against the bare minimum, because the ratio, not the minimum, sets the dose. Published recipes get this wrong constantly: in Stockman 2013, 95 percent of 200 recipes fell short of at least one nutrient, calcium among the most frequent; in Pedrinelli 2017, 73 percent of dog recipes were short of calcium; and in Rosa 2026, 91 percent of recipes written by AI chatbots were low in calcium Grade C. The calcium article on this site shows the dose for three dog sizes.

Iodine and salt: small amounts, easy to miss

Iodine is needed in micrograms, so no recipe looks short of it. The NRC allowance is 29.6 mcg per kg of metabolic weight (German 2015), which is 280 mcg a day for this dog Grade A. About half of 95 raw rations analysed in Germany supplied less iodine than the minimum requirement (Dillitzer 2011) Grade C, and a 2026 case report describes goitre and low thyroid function in a dog fed a home prepared diet without a vitamin and mineral supplement, which resolved on an iodine supplemented food (Lim 2026) Grade C. Petcare does not point at iodised salt, because the salt needed to carry a dog's iodine brings far more sodium than the dog should eat. It asks instead for a vitamin and mineral product supplying at least 280 mcg and no more than 3,000 mcg a day, the upper figure being the AAFCO and EU maximum of 2.75 mg per 1,000 kcal scaled to this recipe Grade A. Chloride is simpler: 378 mg of chloride is 623 mg of table salt, about 1/8 of a teaspoon, which a dog with a heart condition should have confirmed by a vet first.

Vitamin D, vitamin E, zinc and copper: met here, but only just

These four are the nutrients most often short in published recipes, yet food covered them in this one. The reason is that the optimiser chose lamb liver and egg, and it did so with no margin to spare.

When the same dog's recipe is rebuilt with every liver excluded, the solver reaches for 23 g of oysters to hold zinc at 119 percent and copper at exactly 100 percent. A cook who swaps liver for chicken breast has no such step, which is why Pedrinelli 2017 found copper short in 85 percent of dog recipes, vitamin E in 83 percent and zinc in 76 percent, and vitamin D, where short, at a median of 4.4 percent of the recommendation Grade C. Petcare's vitamin D figures likely undercount, because its ingredient data records only the D3 form, so a product adding some vitamin D is sensible. Too much is a real risk: vitamin D toxicosis from a supplement is documented in dogs (Voss 2023) Grade C, and the NRC safe upper limit of 2.62 mcg per kg of metabolic weight, 24.8 mcg a day for this dog, is printed next to every plan Grade A.

A generic multivitamin does not fix a recipe

Owners often assume that any "complete" vitamin and mineral powder closes whatever the recipe misses. The evidence says otherwise. When seven vitamin and mineral supplements sold for home prepared diets were analysed, most did not meet minimums for calcium, potassium, magnesium, sodium, phosphorus, selenium and zinc at their labelled dose, only one had detectable selenium, and three exceeded the mercury safety limit (Zafalon 2021) Grade C. In a chemical analysis of 100 prepared recipes, including a supplement did not ensure a balanced diet (Pedrinelli 2021) Grade C. The recipe itself also drifts: only 4 of 30 owners in one follow up still fed a veterinary recipe exactly as written (Johnson 2016) Grade C. The practical answer is to match the product to the measured gap. Petcare prints, for each nutrient the food could not reach, the least a product must supply per day and the most it may supply, so a label can be checked line by line rather than trusted on its front panel.

Eight common supplements, graded

The grades follow the WSAVA advice to weigh claims by the quality of the dog specific evidence behind them, and to treat anything that sounds too good to be true as exactly that (WSAVA). Two items on the list are required by the nutrient standards themselves. One is a reasonable option. Five have no case in a healthy adult dog, and three of those carry calories or a cost without a measurable return.

Who should not use this list

Everything above applies to healthy adult dogs at a stable weight. Puppies and large breed adolescents have their own calcium and energy needs, and excess calcium harms their skeletons (FEDIAF 2025) Grade A. Pregnant and nursing dogs, dogs on a weight loss plan and dogs with any diagnosed condition need a diet set by a vet, ideally one formulated with a board certified veterinary nutritionist, because a supplement that is right for a healthy dog can be wrong for them. Petcare applies adult maintenance targets and says so on every recipe it prints.

Check it with Petcare

Enter your dog's weight, age and activity in the Petcare calculator to see which nutrients your recipe covers from food and the exact daily amounts the supplement plan adds.

Petcare is software, not veterinary advice. It builds recipes for healthy adult dogs. For puppies, pregnant or nursing dogs, dogs with a condition or food allergy a vet has diagnosed, dogs on medication, and dogs that need to lose weight, the diet should come from your vet.