So what are the signs of nutritional deficiency in dogs? Your dog can’t tell you when something is missing from their diet. But their body will. Dull fur, low energy, digestive trouble, and brittle nails are just a few of the ways a nutritional gap can quietly show up — often long before a vet visit reveals the underlying cause. Nutritional deficiencies in dogs are more common than most pet parents realize, and they don’t only happen in dogs eating poor-quality food. They can occur when a diet is unbalanced, when a dog has absorption issues, or when life stage needs shift and the diet doesn’t shift with them.
Here’s what to watch for, what it might mean, and when it’s time to get professional help.
Why Nutritional Deficiencies Happen
A deficiency occurs when a dog’s body isn’t getting enough of a specific nutrient — whether that’s a vitamin, mineral, protein, fat, or essential fatty acid — over a sustained period of time.
Common causes include:
- Unbalanced home-cooked or raw diets that haven’t been professionally formulated
- Low-quality commercial foods that meet minimum label standards but aren’t optimally nutritious
- Single-protein or elimination diets that inadvertently cut out key nutrients
- Underlying health conditions like inflammatory bowel disease or exocrine pancreatic insufficiency that impair nutrient absorption
- Life stage changes — puppies, pregnant dogs, seniors, and highly active dogs all have elevated needs that a standard adult diet may not meet
8 Warning Signs Your Dog May Have a Nutritional Deficiency
1. A Dull, Dry, or Flaking Coat
A healthy dog’s coat should be soft, shiny, and relatively smooth. If your dog’s fur looks dull, feels brittle, or sheds excessively outside of normal seasonal shedding, it’s one of the earliest and most visible signs that something is nutritionally off.
What it may indicate: Deficiency in omega-3 and omega-6 fatty acids, zinc, or vitamin A. These nutrients are essential for skin barrier function and coat quality.
2. Persistent Skin Problems
Itching, flaking, hot spots, and recurring skin infections that don’t fully resolve with topical treatment can have a nutritional root. Skin is the body’s largest organ and one of the first places nutritional gaps show up.
What it may indicate: Low levels of zinc, B vitamins (particularly biotin and niacin), or essential fatty acids. Protein deficiency can also impair the skin’s ability to heal.
3. Low Energy or Unusual Lethargy
If your dog is sleeping more than usual, reluctant to play, or seems “flat” without any obvious illness, don’t chalk it up to personality. Chronic low energy in a dog that was previously active is worth investigating.
What it may indicate: Iron deficiency (which can cause anemia), B12 deficiency, or insufficient caloric intake overall. It can also signal inadequate protein or carbohydrate sources to fuel daily energy needs.
Are you finding this article useful? Would you like 100% free access to more articles like these, and free access to over 5,000 vetted pet care service professionals throughout the United States? Sign up here for a free Petworks account, and we’ll email you a 10% discount code, good towards your first pet care services booking on Petworks!
4. Digestive Issues That Don’t Resolve
Occasional loose stools happen to every dog. But chronic diarrhea, soft stools, frequent gas, or vomiting that persists without an identifiable cause can point to a diet that isn’t working for your dog’s digestive system.
What it may indicate: Insufficient dietary fiber, an imbalance in the gut microbiome, or deficiencies in digestive enzymes. Some dogs also develop sensitivity to ingredients that displaces absorption of key nutrients.
5. Slow Wound Healing
Minor cuts, scrapes, or post-surgical incisions that take longer than expected to heal can be a quiet signal that the body doesn’t have the nutritional resources it needs to repair tissue efficiently.
What it may indicate: Vitamin C plays a role in collagen synthesis (though dogs produce their own), but more commonly this points to zinc deficiency or low protein intake — both essential for tissue repair.
6. Muscle Loss or Poor Muscle Development
Visible muscle wasting — particularly over the hindquarters, spine, or around the head — isn’t always a sign of old age or illness. In younger or middle-aged dogs, it can signal that dietary protein is insufficient or of poor quality.
What it may indicate: Inadequate protein intake or poor protein digestibility. Amino acid deficiencies, particularly in taurine or L-carnitine, are also associated with heart muscle issues in certain breeds.
7. Brittle Nails or Slow Nail Growth
Nails that crack, split, or break easily — and aren’t the result of trauma or excessive pavement contact — can reflect what’s happening internally with your dog’s nutritional status.
What it may indicate: Deficiencies in biotin, zinc, or essential fatty acids are common culprits.
8. Behavioral Changes, Anxiety, or Poor Focus
This one surprises many pet parents, but nutrition has a meaningful impact on neurological function and mood. Dogs that seem more anxious, reactive, or difficult to focus during training may have a dietary factor at play.
What it may indicate: Magnesium, B vitamins, and tryptophan (an amino acid precursor to serotonin) all play roles in nervous system regulation. Diets very low in these can contribute to behavioral symptoms.
A Note on Puppies and Senior Dogs
Puppies are especially vulnerable to deficiency because their nutritional needs are high and very specific. Calcium and phosphorus imbalances during development can cause skeletal deformities. Too much of certain nutrients can be just as harmful as too little. Puppies should always be fed a diet specifically formulated for growth, and large-breed puppies have different requirements than small breeds.
Senior dogs (generally 7+ years, though this varies by breed) often see reduced gut absorption efficiency, meaning they may not be extracting as much nutrition from their food as they once did. Muscle mass naturally declines with age, making adequate protein quality even more important. A diet that served your dog well at age three may simply not be enough at age ten.
“Nutritional deficiency in dogs is rarely dramatic at first — it tends to show up in subtle, easy-to-dismiss ways. A slightly duller coat, a little less energy, soft stools a few times a week. Pet parents often adapt to these changes gradually without realizing they’re signals. By the time something is obviously wrong, the deficiency may have been present for months. Catching it early, with a proper dietary assessment, makes a significant difference in how quickly the dog recovers.” – — Dr. Marty Goldstein, DVM, Integrative Veterinarian & PetWorks Animal Nutrition Advisor
What to Do If You Recognize These Signs
Don’t panic — and don’t immediately start adding random supplements to your dog’s bowl. Over-supplementing can cause toxicity in some nutrients (vitamin A and D in particular are fat-soluble and accumulate in the body) and can make diagnosis harder.
Here’s a sensible path forward:
- Start with your vet. Rule out underlying medical causes. Conditions like hypothyroidism, Cushing’s disease, and intestinal parasites can mimic or cause nutritional deficiency symptoms.
- Get a dietary assessment. A certified dog nutritionist can evaluate your dog’s current diet in detail — not just the brand, but ingredients, feeding amounts, treats, and preparation methods — and identify specific gaps.
- Make targeted changes, not wholesale ones. Once the deficiency is identified, adjustments can be precise and effective rather than experimental.
- Recheck body condition and coat quality. Most nutritional improvements show visible results within 6–12 weeks, making it relatively straightforward to know if changes are working.
When a Dog Nutritionist Makes the Most Sense
Your vet is an essential first stop, but veterinary training in nutrition is limited. For dogs with chronic skin issues, persistent digestive problems, muscle wasting, behavioral concerns, or those on home-cooked and raw diets, working with a specialist in canine nutrition provides a level of dietary analysis that a general veterinary appointment simply can’t offer.
A dog nutritionist will look at the full picture — diet history, life stage, breed predispositions, activity level, and health status — and create a personalized plan that addresses the root of the issue, not just the symptoms.
If you’ve noticed any of the signs above and aren’t sure where to start, connecting with a dog nutritionist on PetWorks is a practical, accessible first step.
Frequently Asked Questions
Can a dog be nutritionally deficient even on premium commercial food? Yes. Premium doesn’t automatically mean complete and balanced for every individual dog. Some dogs have higher-than-average needs for certain nutrients, absorption issues that reduce what they actually take in from their food, or life stage needs that a standard adult formula doesn’t fully meet.
How quickly does a nutritional deficiency develop? It depends on the nutrient. Water-soluble vitamins (like B vitamins) can become depleted relatively quickly because the body doesn’t store large reserves. Fat-soluble vitamin deficiencies and mineral deficiencies tend to develop more slowly but can take longer to resolve once identified.
Are some dog breeds more prone to nutritional deficiencies? Yes. Certain breeds have known predispositions — for example, taurine deficiency and dilated cardiomyopathy (DCM) has been documented in Golden Retrievers, Cocker Spaniels, and some large breeds. Huskies and Malamutes can have zinc absorption issues. Knowing your breed’s specific nutritional vulnerabilities is a good reason to consult with a canine nutrition specialist.
Should I give my dog a daily multivitamin just in case? Not without guidance. If your dog is eating a nutritionally complete and balanced diet, most multivitamins are unnecessary and some nutrients (particularly calcium, vitamin A, and vitamin D) can accumulate to harmful levels with chronic supplementation. Only supplement based on an identified need.
My dog’s coat improved when I added fish oil — does that mean they were deficient? Possibly, but not necessarily. Many dogs on standard kibble diets are in the low-normal range for omega-3 fatty acids, and fish oil supplementation can produce visible coat improvements without meeting the clinical threshold for deficiency. It’s still worth having a full dietary assessment to understand what else might be suboptimal.
How do I find a qualified dog nutritionist? Look for professionals with credentials such as board-certified veterinary nutritionist (Diplomate ACVN), or certified clinical animal nutritionist designations. PetWorks makes it straightforward to find and connect with vetted dog nutritionists across the United States.
About PetWorks
In 2021, Dr. Marty Goldstein DVM joined the pet care platform PetWorks as an advisor in its Animal Nutrition care division. Dr Marty Nature’s Blend is on a mission to help your pets live their healthiest lives possible. Dr. Marty’s pet nutrition expertise and guidance has helped PetWorks evolve and become the preeminent animal and pet nutrition consultation service for pet parents in North America.
In 2022, Blue Buffalo Founder Bill Bishop Jr. joined PetWorks as Senior Advisor in our Animal Nutrition Care Division. Bill brings his extensive expertise in pet food innovation and business leadership. His guidance strengthens PetWorks’ nutrition offerings. As a result, pet parents everywhere get science-backed support for their animals. This includes expert care for dogs, cats, and more.
PetWorks Co-Founder Kevin Kinyon is a life-long animal lover who works tirelessly to improve the lives of pets and their parents. Human and animal qualities he values most are integrity, humor, and empathy.
