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Like all mammals, dogs produce insulin to regulate their blood sugar levels. When the amount of insulin secreted by the pancreas isn't enough to balance blood glucose levels, this is called Type 1 (or insulin-dependent) diabetes mellitus. Diabetes mellitus should not be confused with canine diabetes insipidus caused by problems with the kidneys or low production of antidiuretic hormone and is not insulin-dependent.

Vets give dogs with diabetes mellitus prescription insulin to supplement or compensate for natural insulin when their body can't meet the demand. Both natural and manufactured insulin work by controlling the amount of glucose that enters blood cells and how much gets converted to glycogen by the liver.

Dosage

The dosage of insulin for dogs depends on the type of insulin prescribed and how much the dog weighs. Some types of insulin for dogs have a starting dose as low as 0.1 units per kg, whereas others have a starting dose of 0.5 units per kg. Typically insulin is given between once and four times a day, depending on the formulation. Always follow your vet's guidelines when administering insulin injections.

Efficacy

The purpose of insulin for dogs isn't to cure diabetes mellitus, but rather to control the symptoms and help their body maintain stable glucose levels. Studies show that insulin is one of the safest and most effective ways of controlling canine blood sugar when administered correctly.

Another clinical study found that when administered twice daily for six months, the dog's blood sugar levels were considerably lower.

Side effects

Below are some of the most common side effects of insulin for dogs:

If a canine's dose is too high, it can cause hypoglycemia (or very low blood sugar) which is equally as concerning as high blood sugar. In rare cases, insulin shock, loss of consciousness, and diabetic coma may occur.

Considerations

As with most medications, drug interactions and reactions can occur when giving insulin for dogs.

Drug interactions

Certain drugs can change the effectiveness of insulin when taken at the same time, Inform your vet if your pet is on any of the following medications:

  • Corticosteroids

  • Asprin

  • Danazol

  • Prozac

  • Fluoroquinolone antibiotics

  • MAOIs

  • Antidepressants

  • Diuretics

  • Oral Hypoglycemics 

  • Isoniazid

  • Anabolic steroids 

  • angiotensin receptor blockers

  • Calcium channel blockers

  • Catapres (clonidine)

  • Diazoxide

  • Blood pressure medications

  • Antiarrhythmic medications

  • Niacin

  • Vasodilators

  • Phenothiazine 

  • Sulfa drugs

  • Somatostatin

  • Thyroid medications

Allergic reactions and sensitivity

Signs of an allergic reaction to insulin include:

  • Hives

  • Itching

  • Facial or body swelling

  • Problems breathing

  • Irritation at the injection site

Frequently asked questions

How long does it take after an injection for insulin to become effective?

Long-acting and intermediate-acting insulins reach maximum effectiveness after 4 to 5 hours. Intermediate insulin wears off in 8 hours, whereas long-acting insulin lasts a full day. Fast-acting insulin formations like Humalog takes effect within 15 minutes of injection and stops working around the 3-hour mark.

Should I skip my pet's injection if they don't eat?

Unless your dog hasn't eaten in 48 hours or more, you should continue their insulin dosage as usual. If you're nearing the 48-hour mark and your dog still isn't eating, call your vet.

My dog just started insulin injections. How long will it take for their glucose levels to regulate?

The time it takes to regulate a dog's glucose levels ranges from a few weeks to over a year, but there are some lifestyle changes you can implement to speed up the process. Making dietary changes and incorporating a daily exercise regimen can help your dog to level out more quickly. 

Will my dog have to take insulin for the rest of their life?

Insulin can be a short-term or long-term solution. The good news is, with insulin, your diabetic dog can live a completely normal and healthy life.

Does my dog need to have a special diet while taking insulin?

Many vets recommend pet parents offer a diet high in fiber and low in fat. High fiber diets slow the absorption of glucose in the body and make insulin more effective. 

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