Am I Over-Supplementing My Dog? What the Numbers Show

Over-Supplementing Usually Starts With One Word: Covering

In most of the conversations I have about supplements in the context of raw feeding, there is one word that comes up again and again. Covering. The thing that comes to the forefront is covering iodine by adding kelp. Covering vitamin D by adding drops. Covering whatever rotation might be missing with a multi-mineral. The word puts kelp and a vitamin D drop on exactly the same footing, which is the problem.

When you hear the word 'covering,' what it sounds like is you are topping off something that is deficient and empty. However, a lot of the dogs that come through with issues don't have an empty bowl. The dog's iodine was already close to the rim before they added kelp, and their third bottle goes onto a shelf already filled a little too full for the owner's liking.

This issue is compounded when people feed fat-soluble vitamin drops. The more they add, the more of their liver is full, but it does not necessarily get safer.

The distance between the NRC 2006 recommended allowance and the safe upper limit is far narrower for fat-soluble vitamins than a supplement label implies. For vitamin D in adult dogs, the allowance is 3.4 mcg per 1,000 kcal and the upper limit is 20 - yet food alone can already sit at 17 before a single drop is added.

Dr. Sarah Missaoui, DVM · NRC (2006), Nutrient Requirements of Dogs and Cats, Table 15-1

Where the Ceiling Sits: A Real Over-Supplemented Stack

Most of the time I start with the iodine, since it seems that most dogs are able to get this close to the NRC 2006 recommended allowance of 220 mcg per 1,000 kcal very quickly. Add kelp four days a week and most of these dogs are at 550-700 mcg per 1,000 kcal. While the thyroid is not going to 'complain' at this level, it will 'drift' and is detectable via blood work long before you would notice anything from a behavioural standpoint.

What I found when I ran the recipe against the bottles

One of my clients had been rotating through 6 proteins along with 'real' organ levels and bone breakdown throughout the week for 18 months with her 3-year-old Malinois. This is a sort of recipe that looks like you have everything handled!

Slowly her stack had 'grown.'

She first added fish oil to the morning feeding, then a kelp product four days a week, vitamin D drops from October through March, and a multi-mineral because 'inland proteins' may have mineral gaps, as was suggested in one of her raw feeding groups.

When we met up regarding her concerns about mild early joint stiffness, she did not have supplements in her mind, but when I looked on my counter they were lined up in 4 bottles.

When I put the recipe's data against the supplements I noted iodine at ~680 mcg/1,000 kcal and Vitamin D at 18 mcg/1,000 kcal. Since the NRC's adult upper limit for Vitamin D is 20, I note that the dog was almost at its max, with just a few mcgs to spare. It only sat that close to the ceiling, rather than over it, because she wasn't rotating any high-fat fish that week.

Fish that included mackerel or sardines, among others, would boost her Vitamin D levels even higher all on their own.

I wrote the numbers down and left them on the counter.

Why Fat-Soluble Vitamins Behave Differently From Minerals

Her initial question for me was should she eliminate everything. At this stage, I could not say 'yes' or 'no' because she had a Vitamin D level of 18 and her 'limit' was 20. The fat-soluble vitamins, A, D, E and K, store in the body and will not get 'washed out' via the urine, and will continue to pool if the 'top off' of the next dose is continued.

The doses do not start at 'zero'; they start at what her body was already carrying from what she had already ingested from the food she prepared.

Furthermore, with an allowance of just 3.4 mcg/1,000 kcal and a max level of 20 mcg/1,000 kcal for Vitamin D, factors such as the fat content of individual protein cuts, whether it's January or July, and which proteins were chosen in the week could alone account for a significant portion of what appears to be needed from drops. I've personally seen food as high as 17 mcg/1,000 kcal before the drops were added.

Reference values: National Research Council (2006), Nutrient Requirements of Dogs and Cats, Chapter 15 (Table 15-1) and the mineral and vitamin tolerance tables. Values are per 1,000 kcal ME for adult maintenance. Calculate your specific rotation rather than estimating from category averages.

The other bottle in her stack was the multi-mineral, in there for the zinc. The reason for adding the multi-mineral wasn't based on evidence that the recipe was already deficient. Rather, the multi-mineral went in out of worry from the previously discussed feeding forum and a general uncertainty.

Unlike vitamin D, zinc does not pool in the liver.

While there are a range of effects that occur at excessively high levels of intake, there is no established ceiling on zinc supplementation for dogs, and a significant volume of liver or red meat would need to be consumed on a regular basis for such a level of exposure. As such, the multi-mineral was not the focus of my attention but the Vitamin D supplements that were next to it.

How to Check Before You Add the Next Bottle

Ultimately, before choosing a new supplement to add, you should have a good idea of how much your dog is currently getting from their diet of meat, organ and bone. Supplement stacks almost never get built in one sitting. Typically fish oil is the first addition, for coat health.

A few months later, something will pop up on a forum or in a magazine, and another supplement gets added.

Six months later, another addition gets placed into the stack. As a result, by the time these supplements arrive on my counter, the client has many reasons to include each item in the stack, and they all make sense individually. However, lost in the individual explanations is the one thing needed, and that is knowing how much was being provided by the meat, organ and bone already in the bowl - the foundation beneath the tower.

This leads to my approach. That starting with the basics, before a single bottle is added to the equation, is the smartest decision. Different dogs will react differently to the same dosage.

The food your 400-kcal eating dog is ingesting versus the food your 1200-kcal dog is eating means their fractions of the top 'plateau' will be different in value.

Nothing from the website listing or your supplement bottle comes in grams, and so this critical calculation is omitted. Without an accurate measure of what the existing diet provides the dog on a per-1,000 kcal basis, the rest of your supplements will only add 'to it' and you will have no idea whether you're bridging a real deficit or simply raising a score which is already well within range. This measurement is what you can actually ascertain before adding any additional supplements.

By the end of our discussion the dog looked excellent, and most of her nutrient values had landed somewhere in range. That was the part that nagged at me. The figure that actually mattered, what the food alone was already handing her before a single bottle opened, wasn't printed on any of the four sitting on my counter.

People Also Ask About Over-Supplementing Dogs

Can you give a dog too many supplements?

Yes. Fat-soluble vitamins (A, D, E, K) and several minerals accumulate when the food already supplies them, so layering supplements on top can push a nutrient past its NRC 2006 safe upper limit. Vitamin D's upper limit is 20 mcg per 1,000 kcal, and raw food alone can reach 17 before any drop is added.

What are the signs of over-supplementation in dogs?

Early excess of fat-soluble vitamins or minerals often shows nothing visible for months; the shift appears on bloodwork before behaviour changes. With larger vitamin D or calcium excess, owners may eventually see increased thirst and urination, reduced appetite, vomiting, or stiffness. Because early signs are silent, the reliable check is the calculation, not the dog's appearance.

How do I know if my dog is getting too much vitamin D?

You calculate it. Add the vitamin D the food delivers per 1,000 kcal to whatever the drops contribute, then compare the total against the NRC 2006 safe upper limit of 20 mcg. Oily fish such as mackerel and sardines raise the food figure on their own, which is why two dogs on the same drops can land in very different places.

Should I stop all my dog's supplements at once?

Not automatically. A supplement that sits within range is not the same as one pushing past the ceiling, and stopping everything can remove something that was genuinely closing a gap. The better first move is to establish the dietary baseline, then decide bottle by bottle which ones the numbers actually support.