Ingredient file // Vitamin or mineral
Monosodium Phosphate
A useful mineral salt with a dose caveat
Monosodium phosphate is a manufactured salt that adds phosphorus and sodium to dog food. It gives formulators a measured mineral source, while short studies of high phosphate diets in dogs raise a question about excess soluble phosphorus.
- What it is
- A water-soluble mineral salt made from phosphoric acid and a sodium source to supply phosphorus and sodium.
- Made from
- Purified phosphoric acid and a sodium source
- Main job
- Adds phosphorus and sodium
- Typical amount
- Not published
- Watch for
- High phosphorus intake in dogs with kidney disease
- Not the same as
- Disodium phosphate
Our read // In our catalog
In 1 of every 52 foods we track
Share of foods that list it
2%
50 of the 2,595 foods with an ingredient list on file, from 15 brands. 49 dry dog food, 1 wet dog food.
Each square is 1% of the catalog
Where it sits on the label
Median position 19.5. In the top five of 0 foods, so it is usually a minor ingredient.
Above the salt
Usually listed after the salt, which caps it at roughly 1% of the recipe in 81% of foods.
Price per lb
Median of the cheapest bag price across 41 priced foods, about level with the catalog. The price is the food's, not the ingredient's.
Who leans on it
30%
of the foods that list it are from Fromm. 15 brands use it in total.
What it is
How it is made
The feed mineral industry makes monosodium phosphate deliberately. Producers react purified phosphoric acid with a sodium source to make a soluble mineral ingredient that feed manufacturers can measure into a recipe.8,9
- 01 // Source Mineral raw materials Purified feed-grade phosphoric acid and a sodium source supply the elements in the finished salt.
- 02 // Process Reacted in granulator A commercial producer reacts the materials under controlled conditions to form granules of monosodium phosphate.
- 03 // Output Feed-grade granules The finished mineral ships in bags or bulk for measured addition to animal feed.
What is in it
Composition, dry matter
20
% phosphorus
Phosphorus in the feed-table grade on a dry matter basis. A small addition can therefore change a food's mineral balance.
Why it is in the bag
What the manufacturer gets
-
01
Sets phosphorus level
A concentrated, soluble salt lets formulators add phosphorus without adding calcium. Its amount must fit the finished food's total phosphorus and calcium balance.4,8
-
02
Adds sodium too
The same addition contributes sodium. It supplies minerals rather than the protein, fat or energy expected from a main ingredient.4
-
03
Adjusts recipe acidity
FDA lists pH control among this salt's technical uses in food. That describes a formulation function, not a demonstrated health benefit in dog food.5
-
04
Ships at production scale
Feed-grade granules are sold in bags and bulk, giving manufacturers a measured mineral input. The commercial product sheet offers no price comparison with other phosphorus sources.9
How much An 18-day dog trial used it in a diet with 1.7% total phosphorus on a dry matter basis; usual kibble inclusion is unpublished.2
Our read // The claims
What the evidence supports
Strong: controlled studies in dogs agree. Some: small or mixed dog data. Thin: mechanism or lab work only. None: nothing, or the evidence points the other way.
-
Brands say
It supplies phosphorus dogs can absorb
Evidence
- Strong
- Some
- Thin
- None
In an eight-dog trial, the diet with soluble monosodium phosphate and soluble calcium had 26% apparent phosphorus digestibility versus 20% for the comparison diet. Both mineral sources changed, so the result does not measure this salt alone.1
-
Vets say
High doses disturb a dog's mineral balance
Evidence
- Strong
- Some
- Thin
- None
Two short studies from the same research group used eight beagles each. High soluble phosphate diets changed after-meal phosphorus and related blood markers. These were marker studies, not tests of long-term disease.2,3
-
Owners say
It prevents bladder stones by acidifying urine
Outruns the evidence
Evidence
- Strong
- Some
- Thin
- None
An eight-dog feeding study recorded after-meal urine pH of 4.9 versus 5.4, but the calcium source changed too. The authors pointed to calcium chloride as an acidifying salt, and the study measured no stones.1
-
Critics say
Any amount of it damages kidneys
Outruns the evidence
Evidence
- Strong
- Some
- Thin
- None
The high-phosphorus dog studies lasted 18 days and measured mineral markers, not kidney disease. They support caution about dose but do not show that every food listing monosodium phosphate harms a healthy dog.2,3
Straight answers
What owners ask
-
Q01
Is it just filler?
NoIt supplies phosphorus and sodium, both parts of a food's mineral balance. It contributes no protein or energy. Its usefulness depends on the finished recipe, especially its total phosphorus.4
-
Q02
Does it mean extra salt?
It adds sodiumThe ingredient contains sodium, but its place on the list does not reveal how much sodium is in the finished food. Ask the manufacturer for the food's total sodium if that number matters for your dog.4,6
-
Q03
What if my dog has kidney disease?
Check the dietKidney care calls for controlling total phosphorus intake. Judge a renal diet by its stated phosphorus level and your dog's treatment plan, not by this ingredient's presence alone.7
Who uses it
Brands, best sellers and the company it keeps
Top brands, by foods that list it
Plus 5 more brands.
Usually listed with, share of the foods that list it
- Chicken Fat 48%
- Chicken Meal 42%
- Lentils 42%
- Chicken 38%
- Brown Rice 34%
- Peas 32%
- Natural Flavor 32%
- Chickpeas 30%
- Pearled Barley 30%
- Oatmeal 24%
- Menhaden Fish Meal 24%
- Flaxseed 24%
Our read // On the bag
Read the whole food's phosphorus level
Low on the ingredient list, monosodium phosphate signals a measured mineral addition, but its position cannot tell you the dose. Check the food's phosphorus level if your dog needs a restricted diet; ask the maker when the bag does not provide it. For a healthy dog, judge the complete food before judging this salt.
Sources
What we read
Checked September 1, 2026.
- 1 Apparent digestibility and calcium and phosphorus in urine after feeding different combinations of calcium and phosphorus sources to adult dogs
- 2 Effects of dietary phosphates from organic and inorganic sources on parameters of phosphorus homeostasis in healthy adult dogs
- 3 The Source Matters-Effects of High Phosphate Intake from Eight Different Sources in Dogs
- 4 Monosodium phosphate hydrate FG
- 5 Substances Added to Food: Sodium Phosphate, Monobasic
- 6 Reading Labels
- 7 Treatment Recommendations for CKD in Dogs
- 8 Monosodium phosphate
- 9 Monosodium Phosphate - Feed Grade