Feline Diabetes Mellitus – Part 1

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Diabetes mellitus (DM) in cats is similar to human Type 2 diabetes in humans. The causes in cats include: • Obesity • Inactivity • High carbohydrate food • Pancreatitis (probably exacerbated by grain in cat food) • Hyperthyroidism • Hypersomatotropism (large cats) caused by excessive pituitary growth hormone secretion. These conditions all increase blood glucose (BG) or insulin resistance. The first four predispositions can be eliminated by feeding grain-free moist cat food. Hyperthyroidism can be controlled. Hypersomatotropism is untreatable at present except at a couple of universities that ablate the pituitary gland using either surgery or stereoscopic radiation therapy.

Pathophysiologically, diabetes mellitus in cats is a combination of chronic hyperglycemia due to the feline deficiency in glucose oxidase and excessive carbohydrate ingestion, and/or thyroid or somatotropin hormone excess, and insulin resistance. Hyperglycemia leads to pancreatic islet beta cell toxicity and exhaustion. Rapidly bringing the BG under control often allows the pancreatic islet beta cells to recover their insulin-secreting ability with resulting normoglycemia.

Diagnosing feline DM

The accurate diagnosis of diabetes mellitus and all complications is essential. Typical history and physical findings are polyphagia, polydipsia, polyuria, weight loss and decreased activity. If the diabetes has been present for many weeks, the cat may show hind limb plantigrade stance and joint sensitivity (pain while being restrained for blood collection). Cats are predictably unpredictable, so some diabetic felines are inappetent rather than polyphagic, more active rather than less, and/or gain weight instead of losing body condition. Often, owners are unaware of increased drinking and urinating. Early cases may have only mild weight loss.

Diagnosis is made on the results of urinalysis, complete blood count (CBC) and differential, serum chemistry and total thyroid (T4) level. A blood glucose above 8 mMol/L = 145 mg/dL is abnormal. If the level is under 11 mMol/L = 200 mg/dL and the cat was stressed by the blood collection, then a confirmation of hyperglycemia is required. Strong glucosuria with some ketones, or a non-stressful ear prick BG, is confirmatory. Very occasionally, we require a serum fructosamine to confirm diagnosis because we are unable to collect a non-stressed blood sample.

In uncomplicated diabetes, the CBC may show a mild stress leukon or leukocytosis. The serum chemistry is generally unremarkable, with mild increases in liver enzyme levels in severe cases. Typically in cats, the alkaline phosphatase level is normal due to its short half-life and urinary excretion. The serum creatinine may show a pre-renal, mild elevation due to dehydration. In a cat losing weight, the T4 should be less than 25 nMol/L = less than 2.0 ug/dL.

Consider T4 levels

When an animal is ill and losing weight, the body’s reaction is to increase stress hormones. This results in adrenal cortical hyperplasia, hyperactivity and an increase in the serum cortisol level. This suppresses thyroid function, causing sick thyroid syndrome. T4 needs to be considered within the context of the patient’s disease status. In a cat with uncontrolled diabetes, weight loss and dehydration, the T4 level should be low; the cat has sick thyroid syndrome.

These thyroid levels overlap so the clinician needs to exercise his/her judgment. With equivocal T4 levels, I recommend re-testing in three months when we have the cat stabilized or recovered.

Early diabetic management

Due to the exhaustion and toxicity of the pancreatic islet beta cells caused by hyperglycemia, diabetes becomes a vicious cycle in the cat. Recovery depends on glycemic control, a low carbohydrate diet, weight loss and increased exercise — the sooner the better. Weight loss and increased exercise are long term projects, but we can rapidly change the diabetic cat to a low carbohydrate diet.

1. Diet A low carbohydrate, high protein diet similar to the cat’s natural diet (i.e. mice), is essential for managing sugar/glucose levels. Approximately 80% of diabetic cats will recover when fed the correct food. This means insulin may not be required at all, or may be discontinued after a few days, weeks or months. Cats that continue to require insulin are better regulated, act normally and need a lower dose than those eating food high in carbohydrates (such as kibble/dry cat food).

Only canned cat food with less than 10% of metabolizable energy from carbohydrates is recommended for diabetic cats. The best food has less than 5% calories from carbohydrates. This information is not available on product labels, however, and very few websites have it – in most cases you must contact the manufacturer, some of whom will reply. To obtain up-to-date information, you can go to Even these foods do not provide reliable low carbohydrate intake. If a cat’s blood glucose levels are “all over the place”, suspect the food and change it.

It is best to feed diabetic cats twice a day, but if you’re dealing with an older, fussy cat that prefers to snack or “graze” all day, the owner can leave the canned food out by adding some water and mixing it into a “cat food soup”. This will prevent the food from drying up and will provide the cat with extra fluid.

Foods to absolutely avoid due to their high carbohydrate content (grains and, in some cases, sugar) include: • Any dry cat food • Dry or soft treats • Any canned food with more than 10% of calories from carbohydrate sources

In addition to low carbohydrate canned cat food, I suggest that owners add some meat, especially cooked or canned fish. Wild salmon and sardines are very low in carbohydrate and rich in the active Omega 3s, EPA and DHA. Most cats love fish. No commercial cat treats are suitable except dried meat. I recommend treats be low carbohydrate canned cat food, meat or fish.

The occasional cat is a dry food addict. For the cat that will not eat what the owner and I select, we try to change the food slowly. If this is unsuccessful, I will prescribe appetite stimulants for three months. I select from Rx Cyproheptidine, Rx Mirtazapine or Rx Clonazepam.

2. Herbs Rapid glycemic control is important for the recovery of feline diabetics, so I recommend that herbs be used in addition to diet and medications. The action of most herbs is to stabilize blood glucose and stimulate insulin release. For Western, Ayurvedic and Chinese herbs, the recommendations are based on human experience; there is no research in cats. The appropriate dose is unknown, and it is often difficult to get herbs into cats because they taste bad.

The most commonly recommended herbal options are: • Ginseng (Panax ginseng) • Gymnema (Gymnema sylvestre) • Fenugreek (Trigonella foenum-graecum) • Bilberry (Vaccinium myrtillus) • Aloe (Aloe vera) • Rehmannia (Rehmannia glutinosa) • Turmeric (Curcuma longa) (References: Veterinary Herbal Medicine by Susan G. Wynn and Barbara J. Fougère and Manual of Veterinary Herbal Medicine by Susan G. Wynn and Steve Marsden.)

3. Rx Glyburide The same caution applies to the oral hypoglycemic medication Rx Glyburide. It increases insulin release and sensitivity, but may not be sufficiently effective at bringing the BG into the normal range to allow the islet cells to recover. Glyburide pills can usually be hidden in the cat’s canned food. It is a sulfonylurea that is safe in cats and has no side effects. The tablets are 5 mg. I start at ½ tablet twice a day, and may go up to one tablet twice a day.

I only use Rx Glyburide if: • The cat is in good condition • The cat is eating well • There are no ketones in the urine • The hyperglycemia is moderate, < 20 mMol/L or < 360 mg/dL • I judge that the diabetes is early or mild • The owner is reluctant to inject insulin into the cat • The owner has financial limits and will not pay for insulin and home BG monitoring

Part 2 of this article (next issue) will cover insulin stabilization with home monitoring; and long-term management and complications.

Feeding cats for health and diabetes prevention

Integrative medicine is most effectively practiced as preventive medicine. In cats, this includes nutrition. In my experience and opinion, the worst thing we can do to damage the health of cats is to feed them dry kibble. Cats are not small dogs. They are carnivores whose ideal diet is four mice a day – approximately 75% water, 15% to 20% protein, a little fat and soluble fiber, 4% carbohydrate (the glycogen within the cells), vitamins and minerals. The mice are consumed raw with digestive enzymes and intestinal bacteria intact, and eaten during the mornings and evenings.

Dry cat food is dehydrated, high in carbohydrates, contains insoluble fiber, is cooked at high temperatures, and is usually fed continually. Why do owners feed such an inappropriate diet to their feline pets? Because it’s convenient.

Four fat mice a day may be the ideal diet for cats, but owners are not about to go this route. The next best cat food is a home prepared raw or cooked diet – also inconvenient for most busy owners and finicky cats. Next best is grain-free canned cat food with some meat offered daily. Most cats will eat some raw or cooked beef, pork, chicken or turkey, or canned or cooked tuna or salmon. Some adult cats are such dry food addicts that they become intolerable if they are not fed some kibble. For these cats, I suggest a maximum of ¼ cup good quality grain-free kibble fed at bedtime.

Domestic house cats are descendants of the African wildcat. As such they are desert animals and generally dislike drinking. I recommend water be mixed into their moist cat food. The quantity of water depends on the cat; everything always depends on the cat. I suggest that owners gradually increase the amount of water they mix into the food, aiming at a 1:1 ratio of moist cat food to water. The goal is that the owners never see their cat actually drinking water, the litter boxes are heavy with urine, and the cat’s urine specific gravity is between 1.020 and 1.030.

In my experience, dry cat food containing grain predisposes cats to many health problems — diseases that can be prevented and often solved merely by getting the cats off this food. These problems include: • Obesity • Allergic reactions – dermatitis, especially around the neck • Alopecia, including lick granulomas • Eosinophilic granulomas • Gingivitis and dental tartar • Gastritis with vomiting; inflammatory bowel disease • Pancreatitis or triaditis • Chronic diarrhea • Diabetes mellitus • FLUTD, bladder crystals (due to chronic dehydration) • Constipation (due to chronic dehydration and insoluble fiber). I am suspicious about chronic dehydration contributing to chronic kidney disease due to the very high urine specific gravity (SG) in kibble-fed cats. These cats often have urine SG >1.080. If nothing else, this results in enhanced levels of toxins and acid in the renal tubules.