Prescription diets

Prescription diets are diets which have been specially formulated to help animals with specific illnesses, they can be used on their own, or with medications. The use of prescription diets has been proven to alleviate symptoms and to prolong life. They are only available from your vet, and must be fed according to veterinary advice, just like medication.

What are ‘Prescription Diets’?

  • Prescription diets can only be prescribed by a vet, they are not available at pet shops, nor can they be bought over the counter
  • Prescription diets are used to help treat many diseases, sometimes your pet will receive extra medication, and sometimes just the diet on its own is enough.
  • Prescription diets are subject to similar rigorous testing at medications, in order for the company to claim the diet is beneficial, they have to prove it does what they say.

How to switch from a normal diet to a prescription diet

Sometimes it can be difficult to change your pet onto a prescription diet, often animals are older and can be ‘set in their ways’. However, there are a few things you can do to help them accept the new food:

  1. If your pet has been poorly with their problem, wait until they get a bit better before offering the diet. If you offer a new food when they don’t feel well, they may associate it with their illness and feeling ill and refuse to eat it, even when they have improved.
  2. Take time to change from one diet to another. Gradually introducing the new food over a period of time, such as a week or more, will be more successful than suddenly feeding the new diet. Every day feed a spoonful less of the old diet, and a spoonful more of the new one, until your pet is on 100% of the prescription diet.
  3. Warming the food can help, especially in cats, as heating the food will release more of its smell, and cats are driven to eat more because of the smell of their food rather then its taste. Increase the food to body temperature. This can also be helpful in animals how aren’t feeling too good and whose appetites have dropped
  4. Adding flavorings to the diet can help, there are several products on the market which are like ‘sauces’ for diets to encourage pets to eat. However, ALWAYS get these from your vet, NEVER add anything to a prescription diet that they haven’t first approved.
  5. There are several different companies who manufacture prescription diets, which means there is some variety available for your pet if they are a fussy eater. Also, most diets come in both tinned and dry varieties so you and your vet can closely match what your pet was eating before.

Prescription Diets


  • Allergies are relatively common in pets and can be to both their food and the environment.
  • Symptoms can include itchy skin, itchy ears, vomiting or diahorrea.
  • Sometimes your vet will suggest blood or skin testing to identify allergens, other times they may just suggest changing your pets food.
  • Prescription allergy diets contain
    • Hydrolysed proteins – proteins in the diet are often what animals are allergic to. Hydrolsyed proteins have been proteins which have been broken down to be very small, too small for the body to be able to react. This means the body physically cannot mount an allergic response.
    • Single sources of protein and carbohydrate – which limits the chance of an allergic response.
    • High in fatty acids – these help to nourish the skin and coat, keeping them in the best of health and meaning your pet is less likely to be itchy
  • Diets contain hydrolysed proteins can be expensive but they are the best thing for an allergic pet.

Brain ageing

  • Senility is a common problem in older dogs, and symptoms include, loss of toilet training, disturbed sleep and disorientation. For more information click here.
  • Hills produce b/d in their range of prescription diets, designed to help animals with signs of senility
  • It contains;
    • High levels of antioxidants which limit free radical damage in the brain,
    • Increased levels of omega fatty acids, which support the functioning of the brain cells, and also
    • Reduced levels of protein, sodium and phosphorus which helps the kidneys and heart, two other organs which can suffer in old age.
  • There is also medication which can help with senility, your vet will advise you on the best course of action.


  • Cancer is sadly very common in pet animals, especially as they age. Veterinary medicine is now very advanced and there is a lot of treatment available including surgery, chemotherapy and radiotherapy.
  • A change of diet in an animal with cancer can be helpful as they have quite specific nutritional needs.
  • Cancer diets have;
    • Reduced carbohydrates – this deprives the tumour of its main energy source, glucose. (The body will break down fat into glucose for energy)
    • High fat – tumours cannot readily use fat as an energy source but the body can. It also means the diets are palatable.
    • Increased protein levels – this means there is enough protein in the diet for both the animal and the tumour. Otherwise the tumour would force the animal to break down their own body tissue.
    • Increased omega 3 fatty acids – this helps to limit the tumours growth and help protect the skin from radiation damage from radiotherapy.
  • The Hills prescription diet n/d has been clinically proven to increase the survival time and quality of life of dogs with cancer, provided they have other treatments as well

Dental Disease

  • There are both prescription and more ordinary diets available for dental care on the market.
  • Dental diets contain;
    • Large kibbles, which means they engulf the teeth as they sink into them, and help to scrape them clean.
    • Kibbles made from a fibre ‘matrix’, which means instead of shattering like normal biscuits as the cat or dog bites, they hold their shape, again meaning they scrape the teeth clean.
    • Slightly low levels of protein and calcium, both of which are needed for plaque and tartar to form.
  • Just because your pet is on a dental diet, it is no excuse for not keeping the teeth clean in other ways, for example brushing the teeth.


  • Diabetes is a relatively common disease that occurs both in dogs and cats, but is more common in cats especially if they are overweight.
  • In dogs, there are no specific diets for diabetes but your vet may suggest a low fat prescription diet as these can help control the fluctuations in their blood sugar levels.
  • For cats, there are several prescription diets available to help with diabetes, and these can help reduce or even eliminate your cats need for insulin
  • Prescription diets for diabetes contain;
    • Low carbohydrate – this helps prevents the peaking of blood glucose after the cat eats, and also encourages the body to burn its fat for energy. Cats with diabetes are often very fat, and weight loss will well them enormously.
    • High protein – this helps to keep the blood glucose levels in the body stable, and also helps the cat maintain good lean muscle mass.
    • Increased arginine – arginine is an amino acid which helps the pancreas to release insulin, which it struggles to do in diabetes.
    • High in antioxidants – free radical damage is common in diabetes and can lead to complications, anti-oxidants reduce the cell damage caused by free radicals.
  • Most diabetic animals will need to be injected with insulin on a daily basis, but the diets can help reduce the amount they need. Some cats can be adequately controlled on diet alone.

Digestive disorders

  • Many animals have sensitive guts, most can be controlled by carefully feeding ordinary diets, but some need to be given prescription diets.
  • Problems which benefit from digestive prescription diets include; food intolerance, pancreatitis, malabsorbtion, colitis and inflammatory bowel disease.
  • These diets are;
    • low in fat,
    • very easily digestible
    • concentrated in energy, so your pet only needs to take in small volumes and the guts aren’t over loaded.
    • High levels of vitamins and antioxidants which maintain the health of the cells of the intestines themselves
    • They will also contain ingredients to help promote a healthy bacterial gut population, which is vital for healthy digestion, and is often out of balance animals with recurrent diarrhoea.
  • Some pets need to be on these diets for only a short time, for example, after a nasty bout of gastroenteritis, but some with more permanent disease need to be on these diets for life.

Heart Disease

  • In animals with heart failure , their bodies can be under a lot of stress and they struggle to cope with a weak heart, the correct nutrition is vital to maintain body condition.
  • Heart failure diets have;
    • Reduced salt levels – this helps to decrease the fluid retention which is very common in heart failure and puts huge pressure on the heart.
    • Increase potassium – potassium is vital for good heart function, and is often decreased in heart failure, especially if animals are on medication.
    • Increased taurine and L-carnitine – these amino acids are both vital for the heart to be able to contract fully.
    • Decreased protein and phosphorus – having heart failure increases the risk of kidney failure, low protein and phosphorus help protect the kidneys and lessen the risk.
    • Calorie concentrated – animals with heart problems are often have small appetites and are prone to losing weight. High energy diets mean good palatability and they only have to eat a small amount to get all the calories they need.
    • High in antioxidants – heart failure patients are particularly at risk from cell damage by free radicals, antioxidants protect against them.
  • With heart problems the first line of treatment should be medicine, which your vet will prescribe, but diet is also very important.

Joint problems

  • Arthritis and other joint problems are common in pets, and is seen in both older animals with arthritic joints and younger animals with developmental problems or juvinile arthritis.
  • Joint diets are relatively new additions to the prescription diet market, and many claim to reduce your pets need for supplements and medication, which can make it an economical choice.
  • Joint diets contain;
    • High levels of essential fatty acids – these have been proven to reduce the inflammation in damaged joints, and help make animals more comfortable.
    • High levels of anti-oxidants – the inflammation in joints can be very destructive, anti-oxidants help limit this damage and aid joint repair.
    • Added supplements – joint diets generally contain added supplements for joint support, such as glucosamine, chondroitin and green tipped mussel extract.
    • Low fat – it is very important animals with poor joints do not become overweight, as the more weight they carry, the more strain is put on the joints.
  • Animals with joint problems will often need medication and supplementation to keep them comfortable but joint diets are also very helpful in the fight against arthritis.

Kidney Disease

  • Kidney disease is very common in older pets, especially cats, and dietary change is the mainstay of treatment
  • The kidneys are non-regenerative organs, so treatment is aimed at supporting the remaining portion of the kidneys by reducing their work load and preventing any further damage.
  • Kidney diets have;
    • Reduced levels of protein – when the body metabolises proteins, toxic waste products are formed, which the kidneys excrete. Reducing the level of protein, reduces these toxins and hence the pressure on the kidneys
    • Reduced levels of phosphorus and sodium – the kidneys will also excrete any excess of these minerals, and in high levels both can be damaging to the kidneys.
    • Increased potassium – potassium levels can fall in kidney disease as the kidneys should retain it for the body, low levels can be damaging to muscle and the heart.
    • Increased omega 3 and 6 fatty acids – these act to reduce any inflammation in the kidneys and also increase the blood flow to the kidneys.
    • Increased B vitamins – these can be lost in large volumes in kidney disease, and are vital for many body functions.
  • Kidney diets should also be very palatable as animals with kidney disease often are not keen to eat.

Liver disease

  • Liver disease is common in pets, more so when they age, but it is also seen in younger animals with developmental problems or hereditary disease.
  • The liver is the metabolic powerhouse of the body, and involved almost every bodily function, it is also regenerative, so given the right support it can repair damage to itself.
  • Liver diets contain:
    • Very high quality proteins – the liver breaks down the protein in the diet for the body to use, having high quality proteins in the diet means the liver has less work to do to make them suitable for the body.
    • Increased Vitamin K , zinc and potassium – these can be very low in liver disease and are vital for many body functions.
    • Low sodium levels – high salt levels can increase the blood pressure in the liver and also cause fluid retention.
    • Low copper levels – some forms of liver disease are associated with copper build up in the liver, low levels help prevent this happening.
    • Supplemented L-carnitine – L carnitine is an additive which means it is easier for the body to use its fat resources as energy. The liver uses a lot of energy and this means it doesn’t have to use its own stores, which places more pressure on it.
    • High levels of anti-oxidants – these help to reduce free radical damage on the cells of the liver.
  • Liver diets tend to be very palatable and are available in both wet and dry versions. They help the liver by meaning it doesn’t have to work so hard to provide for the body, and also provides the nutrition it needs to repair itself.
  • Your vet may also prescribe medication for liver disease.


  • Obese animals are at risk from a huge range of heath issues, including joint problems, heart disease, diabetes and cancer
  • Recent research has proved that obese pets can live up to 2 years less than animals of a normal weight.
  • There is a large range of light or low fat foods on the market, but some pets benefit from a prescription diet especially for losing weight, particularly if they are very fat or have struggled to lose weight.
  • Obesity diets contain;
    • Low fat – this encourages the body to use its own fat stores for energy.
    • Increased protein – this helps the aminal to maintain their lean muscle mass and also makes these diets palatable.
    • High fibre – this bulks out the diets, making the animals feel full without them consuming large amounts of calories.
  • It is important to follow the feeding guides given by your vet, and check your pets weight regularly when they are on these diets.
  • Once your pet has lost the weight, your vet may then move them onto a more standard low fat diet.

Urinary disorders

  • Urinary problems are common in pet animals, and will often present as cystitis; producing urine little and often, painful urination, blood in the urine, or the animal cleaning their vulva or penis more ferquently.
  • Urinary problems can be cause by several different things, bacterial infections, prostate problems, idiopathic bladder crystals or stones or (meaning no know cause) which is common in cats, and is often stress related
  • Urinary crystals and stones are caused by the minerals in the urine clumping together. They damage the bladder lining and cause a painful cystitis.
  • If your animal is diagnosed with urinary crystals or stones, your vet may well advise your animal goes onto a prescription diet, which one depends on what kind of crystals or stones are present.
  • Urinary diets contain:
    • pH modifiers – most crystals or stones can only form when the urine is a certain acidity or alkalinity. These diets help maintain the urine pH at a level at which they are unlikely to form
    • Increased sodium – this encourages the body to produce more urine, which has a flushing out effect on the bladder. This means crystals have less time to form and less time to cause any damage to the bladder.
    • Reduced phosphorus or calcium – the two most common kinds of crystals or stones are made predominantly of phosphorus or calcium. Low levels of these in the diets means there is less in the bladder from which the crystals can form.
    • Low magnesium – again, magnesium is required for crystals or stones to form, lower dietary levels means they are less likely to recurr.
  • Some crystals and stones, most commonly struvite, can be dissolved and cured with diet alone. Others, most commonly calcium oxalate, cannot be dissolved by diet, and may need initial surgery to remove, followed by dietary change to stop them reforming.

Please note this is an advice only website, if you have any specific concerns or queries about your pet, you should contact your vet.

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