Does My Dog Have a Vitamin Deficiency?

I am writing this blog today because I keep seeing a bashing of the use of supplementation of vitamins and minerals for your dog and I think it can become confusing and taken out of context. I wanted to create a whole picture of your dog’s health, the nutritional profile of food, common deficiencies, genetic mutations and malabsorption issues, that can affect this entire picture of health and where deficiencies can most certainly lead to concerns such as poor digestion, skin issues and disease. I am not an advocate of throw it in and see happens, but I am an advocate for addressing nutritional shortfalls in a diet that can most certainly lead to other issues if left unturned. So this blog is about balance, retrospect and highlighting that there isn’t always a generic approach to feeding.

Food supplements are an umbrella for functional ingredients whether they are wholefoods, probiotics, fatty acids or vitamins and minerals. Food supplements are big business and rightly so as certain supplements can offer unique and effective support in some cases. Many of us may know about chamomile and valerian for calming, medicinal mushrooms for immune support, glucosamine and green lipped mussel for joint support and probiotics for digestive support and immunity. The list is endless when it comes to wonderful supplements we can use, some of great quality and efficacy and some not so great. Supplements are a wonderful addition to a healthy diet if used correctly and can support disease. Today I wanted to mention the use of vitamins and minerals and the controversy surrounding them.

Gut Guardian

Vitamins and minerals, unless from wholefood source, and believe me I’ve been in the industry long enough to know this process is far from the ‘wholefood’ dream you are sold, are derived from a number of sources that may be deemed synthetic. This seems to be a dirty word in the industry at the moment and without people knowing much about it, they tend to give it a bad wrap. Whilst I am not an advocate of overloading the body with additional vitamins and minerals, I do know how transformative they are when used in deficiency or disease and also in some cases, prevention. Foods nowadays don’t tend to provide the levels of nutrients expected and required from what we call a balanced diet. This is why it’s become such a huge industry in the health sector. Looking at pets, this trend closely follows.

Due to agriculture, farming and depleted soils, food doesn’t always offer the nutritional profile we are led to believe (no one meat source or vegetables will contain the same amount of vitamins and minerals). Creating recipes is something I have to do on a weekly basis. I love working with the power and transformative therapy of food but I do on occasion like to ensure a little added vitamin and mineral are provided when I know it is something that often shows up as a deficiency due to depletion or that a particular dog will require additional support. For example, there are some beautiful zinc rich foods that you can include in your dog’s food on a daily basis if you create your own food at home. Whether this be from oysters, pumpkin seeds, venison and other red meats but as a formulator of foods, it’s easy to see how many meals, even over time, don’t quite hit the mark for the amounts required by dogs. Research has proven that zinc is one of the hardest minerals to absorb due to it being pipped to the post by so many other minerals and around 60-85% of zinc in the diet is not well utilised and absorbed. I hope I am painting a fair picture here, it’s simply about balance and looking at possible shortfalls.

In my practise, I work with due diligence and a fine tooth comb. As a functional medicine practitioner, I work off a grid that maps all bodily systems over a 12 page questionnaire. We look at this sytem as well as history, presenting symptoms and possible diagnosis. I would call it a jigsaw puzzle that I piece together, trying to fill in any missing pieces. I can quite often tell if there is a deficiency but I do often work with tests to make sure the more dangerously stored nutrients such as A,D,E and K are tested. Unfortunately there is poor testing for minerals and whilst some might still offer blood tests, this often gives inaccurate readings unless your dog is at death’s door. There are a number of symptoms associated with deficiencies that when taking in the whole picture of health, can often tell you a lot about the pathophysiology and the health state of your dog.

Fresh foods are incredibly important for a number of reasons. They provide enzymes, antioxidants, phytonutrients and fatty acids that are all essential for good health. Vitamins and minerals are only one factor and aspect when we look at ‘nourishment’. However, vitamins and minerals are incredibly important and involved in 1000’s of biochemical pathways in your dog’s body. Whilst food source is always preferable, we can see that there can be many reasons for dog’s not to absorb effectively. The most common deficiencies I see in clinic today are vitamin B9, vitamin B12, vitamin D, magnesium and zinc. Obviously this is not exclusive, just my overall experience.

Reasons for nutritional deficiencies

Poor commercial food

I don’t even know where to begin. Most foods are so void of any nutrition after they have been cooked to high temperatures, several times over, a premix of vitamins and minerals have to be added to provide any nutrition at all. This isn’t good basic nutrition and i am not a fan of any commercial food unless home cooked style or raw.

To further the problem even more, many commercial pet food in the EU do not fulfil nutritional requirements. Only 6% (6/97) of wet and 38% (30/80) of dry food were fully compliant in a 2017 study of around 177 food brands. Some foods (20–30% of all analysed) had mineral imbalance, such as not having the recommended ratio of Ca:P (between 1:1 to 2:1). Foods with high fish content had high levels of undesirable metal elements such as arsenic. This study highlighted broad non-compliance of a range of popular pet foods sold in the UK with EU guidelines (94% and 61% of wet and dry foods, respectively). If fed exclusively and over an extended period, any commercial food can imply health concerns.

Findings here


Low grade, constant stress experienced by your dog, releases a continuous and poisonous level of cortisol that leads to inflammation. This cortisol levels tend to shut down the digestive system as your dog goes into a fight or flight mode. This impairs digestion, assimilation and absorption of nutrients.

Nutritional profile of fresh food

Feeding a balanced and FRESH diet whether raw or cooked is the best option for your dog hands down. It is imperative that balance is provided over time and doesn’t have to be regimented everyday. Obtaining nutrition from unadulterated fresh food is by far the best but we know that all foods are not created equally, we can only qualify and quantify up until a point.

Ultimate Guides

Imbalanced gut flora and possible leaky gut can lead to inflammation and poor absorption of nutrients. These issues often arise from poor foods, allergies and intolerances, stress, over sensitive immune systems, constant vaccinations, chemical monthly treatments and so on. Taking care of these factors in order to support and preserve a well functioning gut is essential to nutrient absorption and general immunity.

Sensitivities and allergies

As mentioned from above, this requires a note of it’s own as making sure the digestive immunity is functioning effectively is core to gut health.


Colitis and Crohns disease are probably the most common disease to think of in terms of malabsorption but many disease including thyroid, pancreatitis and other endocrine dysfunction can contribute to vitamin and mineral deficiencies.


Methylation genetic mutations (conversion of folate to methyl folate is essential for overall health). Certain genetic mutations known in humans and dogs, can prevent this from happening and often the only resolution is to supplement ‘methyl folate’ into the diet. Poor methylation is linked to neurological disease, cardiovascular disease, reproductive disease, miscarriage, kidney disease, digestive disease, detoxification issues, cancer and more. So if folate (B9) is not converted to methyl folate to allow for methylation to occur in DNA synthesis, your pet is probably not going to achieve good health during longevity.

I had a female, dog come to me who had thyroiditis, skin issues, concurrent miscarriages and high cholesterol. Whilst there was a lot of inflammation going on for that dog, a supplement of methyl folate and a few other nutrients meant the thyroid function went back to normal, cholesterol lowered, skin cleared up and energy peaked again. this dog had been to see four other specialists over a period of 2 years with no avail. It was a simple nutritional deficiency that was overlooked. We also suspected low zinc of which we supplemented to see skin issues disappear.


May cause malabsorption of certain nutrients. Some drugs can deplete nutrients by speeding up the metabolic process. For example PPIs (antacids) have shown to interfere with gut microbiota and vitamin B12 absorption.
Whilst it is about an all rounded approach to health and the most fundamental part being a fresh food diet, we can’t deny the importance and possible use of vitamins and minerals on occasion, when considering the above.

Common deficiencies seen at My Pet Nutritionist

Vitamins B9

The effects of folic acid deficiency on immunity have been more thoroughly investigated in animals and the antibody responses to several antigens have been shown to decrease. As de novo synthesis of methyl groups requires the participation of folic acid coenzymes, the effect of folic acid deficiency on pancreatic exocrine function was examined in rats (Balachi and Wagner, 1992; Balaghi et al., 1993). Pancreatic secretion was significantly reduced in the deficient group compared with the pair-fed control groups after five weeks.

Deficiencies of choline, vitamin B12, iron and vitamin C all have an effect on folic acid needs and absorption. Folic acid is abundant in green leafy materials and organ meats and sometimes in a better bioavailable form. Deficiency signs don’t generally develop unless bacterial synthesis in the intestine is compromised through antibiotics, stress and poor food. Signs of deficiency can results in loss of appetite, watery exudate from eyes, glossitis, leukopenia, hypochromic anaemia and decreased antibody response to infectious canine hepatitis and canine distemper virus (NRC, 2006).

Vitamin B12

B12 is essential for a healthy nervous system and brain function, as well as for the formation and growth of blood cells. It’s also involved in intestinal health, so your dog needs B12 to maintain healthy digestion. Many of dogs generally absorb B12, however with leaky gut, digestive disorders (lack of instrinsic factor that helps manufacture B12 in the intestines) or other health issues, they may not be able to absorb the desired quantities. B12 rich foods are meat (especially organ meat), fish, poultry and eggs mostly. Dogs with a B12 deficiency and/or anaemia may experience diarrhoea, lethargy, loss of interest in life, loss of interest in food, weight loss anaemia, and in serious cases, seizures.

Therefore, diseases of the pancreas such as EPI (exocrine pancreatic insufficiency) and pancreatic cancer In all dogs, the pancreas plays a vital role in the extraction of B12 from food. Intestinal Cobalamin (B12) Malabsorption is a genetic mutation originally found in border collies and still prevalent in this breed and others. Gut microbiome plays a huge role in B12 synthesis so poor gut bacteria can play a HUGE part in B12 deficiency. Obviously servicing gut bacteria is the best option for longterm support but supplementing is key when a deficiency is demonstrated.

Vitamin D

Vitamin D is a really big vitamin for showing up as deficient and usually chronically at around 70% of all dogs tested showing deficiency. Vitamin D comes in two sources. D2 primarily found from plant sources and vitamin D3 (the most bioavailable form for dogs) usually comes from fatty fish, meats and liver. Dogs absorb less from the sun as humans and rely on diet mostly. That said, being fat soluble and a vitamin that likes to store in the liver, over supplementing in your dog’s diet, can be dangerous if values are tested.Vitamin D is stored in adipose and muscle tissues, and cytochrome P450 enzymes convert vitamin D to 25-hydroxyvitamin D (25[OH])D) in the liver. As one of the most stable vitamin D metabolites, with a long half-life of 10 to 21 days, 25(OH)D is commonly measured in humans and animals as a marker of vitamin D status and low levels are associated with disease, including cancer.

Although rich foods are salmon, sardines, dairy, eggs and mushrooms mostly, the nutritional profiles of these foods can vary greatly. Also being a fat soluble vitamin means it is harder to absorb and in my opinion when looking at foods on the market, are often rather low. Vitamin D offers so much to your dog, it helps in in calcium and phosphorous metabolism for bone health, supports immunity, hormonal function. Chronic kidney disease (CKD) is linked to impaired vitamin D metabolism because the metabolite 1,25(OH)2D is produced in the kidneys. Dogs with CKD often shows decreased blood and serum 25(OH)D concentrations. IBD (inflammatory bowel disease)  often demonstrate low vitamin D blood serum and research shows significantly lower levels compared with healthy dogs.

There has been a huge amount of research around vitamin D and cancer. Research has demonstrated low serum levels in canine osteosarcoma and mast cell tumours. The tissues possess vitamin D receptors, and decreased vitamin D status is associated with additional canine cancers, including lymphoma.

Deficiency can show in lethargy, excessive thirst, excessive drooling, joint disease and weight loss. A test must always be given as high dose can be dangerous. It is a hard one to monitor as scientists can’t measure the important form of vitamin D, only the measurable its precursor (25VitD) so we don’t fully understand how it is utilised. However, I like to work with medium levels and look for outward signs as well as low 25VitD levels.


Magnesium alone serves around 500 biochemical pathways in the body. I saw a client not long ago who had been to every behaviourist for a dog who had the worst anxiety and pain but according to the vet was idiopathic. The dog also had anal gland issues caused by slow transit in the digestive tract with sever constipation. This dog was on a raw food diet and had seen countless natural supplements for digestion. I immediately knew the vagus nerve between the gut and the brain was not functioning well due to slow transit, anxiety, tight muscles and tremors. We looked at serum b9 (methyl folate), b12 of which did not register on the blood panel they were so low and then put in magnesium taurate to ease the anxiety. This beautiful boy can now sit, relax, be stroked, go to the toilet with a healthy stool everyday and enjoy life as was intended.

Magnesium deficiency in dogs has been associated with neural and neuromuscular hyper excitability in research and signs can include tetany, muscle spasms, fasciculations, and tremors. in a 21st century home magnesium is required in constant supply. Magnesium helps support stress but is also depleted by stress doe to neurological overload. Magnesium doesn’t always come in concentrated amounts in food. Rich foods would be green leafy veg, nuts and seeds (hempseed is very good), fruit such as bananas, salmon and mackerel mostly. This is mineral that even when balancing food nicely, can become depleted rather quickly.

Findings here


Deficiency of zinc in genetic mutations are mostly affected by Huskys and Malumutes but I have seen the genetic mutation in other breeds. Zinc is an incredibly difficult mineral to assimilate and is a common mineral to be deficient as it competes with other minerals ineffectively. I often recommend to take at night before bed (in humans), so it can’t be competed against. The issue is, zinc is essential for pretty much everything, considering it’s partly responsible for healthy DNA and cell replication. If DNA synthesis doesn’t occur correctly, cells aren’t produced properly and whilst this can outwardly show issues with skin for example, internally this can be a big contribution to disease such as cancer. Zinc works alone and with other nutrients. It has a close synergy with copper which if deficient can create a copper toxicity (seen in some liver disease). It works alongside B-complex vitamins (mostly B9 and B12), vitamin A, calcium and phosphorous, to support the body, immunity and help hundreds of other functions in the body.

If your dog has immune reactions such as sensitivities, allergies and skin irritation, crusty raised skin patches or pustules, poor digestion (leaky gut), an under functioning thyroid, seizures and odd behaviours, these can all be due to a zinc deficiency.

Everyone should tread with caution, I am not suggesting we all supplement our dogs with zinc, as over supplementation is also bad for health. I am saying however, leaving a deficiency has longterm implications. Zinc citrate, picolinate, gluconate and methionine are highly absorbable and good forms. Overloading your dog’s body with zinc can also create other imbalances so only seek advice if you feel any of the aforementioned applies to your dog.

If you are unsure if your dog’s is lacking in zinc or any other nutrient, consult a nutritionist before supplementing.

I hope this has helped. Whilst I advocate a fresh and varied diet for dogs, it does sometimes happen that deficiency can occur. I needed to write this blog as i believe not supplementing as well as supplementing blindly can be damaging. In an ideal world we would not have to resort to any supplements (this includes probiotics, fatty acids and so forth), but this in my experience of nutrition, is not always possible.

If you want to know more about our consultations, please check us out.


MPN Team x

Keep up to date

Subscribe to our newsletter for recipes, DIY products, health solutions and more.

You have been successfully Subscribed! Ops! Something went wrong, please try again.

Customer Reviews

Related articles