Diabetes: Yes, dogs get it too

As you'll know, diabetes mellitus (DM) is a very common condition in people, but you might not be aware that it's also common in dogs

Unfortunately, common doesn't always mean easy. According to the American Animal Hospital Association (AAHA):

Diabetes mellitus (DM) is a treatable condition that requires a committed effort by veterinarian and client. Due to many factors that affect the diabetic state, a pet’s changing condition, and variable response to therapy, management of DM is often complicated.

Success requires understanding of current scientific evidence and sound clinical judgment. Each patient requires an individualized treatment plan, frequent reassessment, and modification of that plan based on the patient’s response.

Now, that quote isn't meant to scare you – most diabetic pets do well and live good lives. But you do need to be prepared to manage some possible bumps in the road.

Let’s have a look at canine DM in more detail.

What is diabetes mellitus?

DM is a complex metabolic condition with the hallmark feature of high blood sugar (or glucose).

Note: In Australia, blood sugar is measured in units called millimoles per litre (mmol/L). You might see American info that uses milligrams per deciliter (mg/dL).

We all have some sugar in our blood, it's an important fuel source. It comes from two main sources:

  • carbohydrates in the food we eat

  • conversion of non-carbohydrates by the liver (a process called gluconeogenesis) 

The amount of sugar in the blood is usually pretty tightly controlled (between 4–8 mmol/L). This control is achieved by the action of several hormones, the main one being insulin. Very simply, when blood sugar rises, insulin is released (by the pancreas) and acts to move sugar from the blood into the cells (where is it used for energy immediately or stored as an energy source for later – as glycogen or fat). When blood sugar goes down, other hormones such as glucagon and cortisol are released and these stimulate the liver to make some more sugar and release it into the blood. 

Diabetes (high blood sugar) is due to either:

  • a lack of insulin – the pancreas stops making it due to immune-mediated destruction of insulin-producing cells (this is referred to as type 1 diabetes in people and is the sort dogs get)

  • insulin resistance – where there is enough insulin but the tissues stop responding to it (this is type 2 diabetes in people), eventually this can lead to insulin deficiency as the pancreas becomes dysfunctional and struggles to continue to make insulin (this is the sort cats get)

So whether you've got type 1 or type 2 diabetes, you've got a problem with insulin, which causes increased blood sugar.


Without insulin, the sugar in the blood can't get into the cells. The cells don't get enough energy and so they send out 'I'm starving' signals, which results in one of the signs of diabetes – increased hunger.

The body tries to feed the starving cells by increasing gluconeogenesis in the liver, causing breakdown of body protein and fat, resulting in another sign of diabetes – weight loss.

But no matter how much food is eaten or how much body tissue is broken down, the sugar still can't get into the cells so the body switches to an alternative energy source called ketones. High levels of sugar and ketones in the blood is a life-threatening condition called ketoacidosis. (NB: ketosis and ketoacidosis are different things)

At a certain level of blood sugar, the kidneys stop retaining it and instead they allow sugar to go out in the urine. When this happens, the sugar in the urine draws extra water out with it, causing a loss of body water and increased urine production. Hence, the other two main signs of diabetes – increased urination and increased thirst (to make up for the water loss).

In people, the excess sugar in the blood has a negative impact on numerous tissues, particularly blood vessels (large and small) and nerves. Over time, this results in things like blindness (diabetic retinopathy), cardiovascular disease, nerve damage (diabetic neuropathy). Fortunately, dogs don't tend to get these sorts of complications very often – but (unfortunately) that's probably just because they don't live as long as people. Dogs with diabetes can go blind, but this is due to cataract formation.

What causes diabetes?

Diabetes in dogs is the result of damage/destruction of insulin-producing cells in the pancreas. The main cause of damage is the body's own immune system. For reasons we don't yet know, the immune system stops recognising the insulin-producing cells as belonging to the body and sees them as foreign agents that need to be destroyed. Once this process has started, it cannot be reversed, so these dogs will need insulin supplied (via injection) for the rest of their lives.

We do sometimes see diabetes occurring after a condition called pancreatitis. It is possible for the cells to recover after this and so this may not be permanent.

What are the symptoms of diabetes?

We've pretty much covered these while looking at what diabetes is. The key symptoms to look out for are:

  • eating a lot (polyphagia)

  • drinking a lot (polydipsia)

  • peeing a lot (polyuria)

  • weight loss

When diabetes first develops, these symptoms may be extremely subtle and your dog will seem well. As the disease progresses, the symptoms become more obvious but dogs can still seem well until ketoacidosis develops.

Symptoms of ketoacidosis include:

  • lethargy

  • anorexia

  • vomiting

  • dehydration

  • acetone breath (not everyone can smell this so don't rely on it)

It's really important to notice things before ketoacidosis occurs because it's much more complicated to treat (requires fairly intensive in hospital care) and despite treatment, some dogs will still die.

How is diabetes diagnosed?

Diabetes is usually pretty straightforward to diagnose. In a dog with clinical signs, we look for:

  • high blood sugar (hyperglycaemia)

  • sugar in the urine (glycosuria)

When we're assessing a dog for diabetes, we tend not to just check blood sugar and urine glucose. This is because dogs with diabetes frequently have concurrent diseases, such as pancreatitis and urinary tract infections. And we need to check for evidence of ketoacidosis.

When diabetes is suspected/diagnosed, we may recommend:

  • haematology and biochemistry (blood testing)

  • complete urinalysis (possibly with culture)

  • abdominal ultrasound or pancreatic lipase testing for pancreatitis

How is diabetes treated?

The main goals when treating diabetes are:

  • reduce or resolve clinical signs using a treatment regimen that fits into your daily life

  • avoid low blood sugar events (hypoglycaemia)

  • prevent complications (eg diabetic ketoacidosis)

To achieve the first goal, we need to reduce the elevated blood sugar levels, typically through insulin therapy. Oral medications used by people with diabetes have been used in dogs, but they don't tend to work well and come with lots of side effects.


Cats and people can often manage their diabetes (type 2) with diet alone. This isn't the case in dogs, but diet is still important and there are some basic principles that hold true for the dietary management of diabetes for all species, including:

  • the food must be tasty enough to be reliably eaten – to control blood sugar with insulin injections, we need the patient to eat on a regular schedule 

  • the food must be of quality and quantity to maintain good body condition 

The ultimate goal is to feed two similar meals a day (approximately 12 hours apart) with less than 10% of nutrients coming from treats. Insulin is given within an hour of each meal (lots of people give the injection while the dog is eating).

A diet rich in fibre can be helpful to blunt the effect of blood sugar rise after eating. There are two sorts of fibre: soluble and insoluble. With diabetes, we want more insoluble fibre than soluble. The dietary panel on food packets probably won't tell you anything more than just 'fibre' (where you should look for something around 10% of dry matter). The ingredient list can help you work out what sort of fibre the food contains. Soluble fibres include beet pulp, guar gum, psyllium and fructooligosaccharides. The main insoluble fibre is cellulose.

Because of the relationship between pancreatitis and diabetes, a diet lower in fat is recommended. 

There are several commercial diets used for diabetes (eg Hill's W/D and Royal Canin Satiety). If you'd prefer to do a home cooked diet, we recommend using BalanceIT (Free Autobalancer EZ for Vet Patients) to help get the nutrient balance right. 


Yes, that means injections. Unless you have a needle phobia, it will only take a couple of injections for you to get used to giving the insulin.

The aim of insulin isn't to get the blood sugar back to normal. We're aiming to:

  • get the blood sugar below the level where sugar spills into the urine (ie <14 mmol/L) for as much of each 24 hour period as possible

  • avoid low blood sugar (<4.5 mmol/L) at all times (low blood sugar is called hypogylcaemia – see below)

The most common sort of insulin used for dogs is Caninsulin. It's an intermediate-acting insulin lasting somewhere between 12 and 24 hours in dogs. One important thing to note about Caninsulin, as opposed to almost all other sorts, is that each millilitre contains 40 units of insulin (others contain 100 units). Only insulin syringes calibrated to 40 units/ml can be used with Caninsulin – these come with a red cap. Note: instead of millilitres (mls), insulin is measured in units.

The starting dose is low and depends on how high the blood sugar is (as well as size of dog).

Insulin is usually given twice daily. While rigidly adhering to 12 hourly injections might be ideal, real life tends to get in the way. The latest guidelines allow for a more flexible approach with injections being given every 10–14 hours (ie 12 hours +/– 2 hours) and simply missing an insulin injection if other commitments prevent dosing at the correct time.

To give insulin injections:

  • first, feed your dog – if you give insulin and your dog doesn't eat, the blood sugar may drop dangerously low

  • before drawing up the insulin, roll the bottle back and forth so that the white material in the bottom is mixed well into the rest of the solution

  • hold the bottle vertically, with the stopper at the bottom (this prevents drawing up air bubbles in the syringe) 

  • push the needle through the stopper and draw up the prescribed amount (if you do get air bubbles, you can inject everything back into the bottle and then try again)

  • lift up a fold of skin (anywhere on the body), which creates a 'window' for the needle

  • insert the needle into this fold and inject the insulin

  • withdraw the needle and carefully replace the cap (or put it straight into a sharps container)

Lots of people reuse insulin syringes for their pets. While ideally, we'd only use them once, we see very few issues when people do reuse insulin syringes and it can save money. As the needle becomes more and more blunt each time it passes through the bottle stopper and the skin, you'll probably have to change it at least every 2–3 days. Blunt needles hurt much more than sharp!

Here's a video of how to give a dog an injection.


It may be that the starting dose works well to control your dog’s symptoms. If the symptoms are controlled and weight has stabilised, we might just stick to that dose unless problems arise. 

Typically, after starting insulin, we stay on the initial dose for around 7–10 days (or more) before we even consider adjusting it. If and how we adjust the insulin dose depends on symptom control (most important) and on blood sugar levels at different times during the day. The rise and fall of blood sugar throughout the day (and night) is called the glucose curve.

In a typical glucose curve, the blood sugar is usually highest (the peak) in the morning before the first injection then drops to its lowest (the nadir) around 6–8 hours later. It then rises again until the evening injection. 

To graph a glucose curve, blood samples are taken every 2–4 hours starting as close to the morning injection time as possible and finishing close to the evening injection. In cases where we're concerned that the blood sugar might be going too low (hypogylcaemia), we might take samples every hour around the nadir so that we don't miss a dip. 

Blood glucose curves can be done either by us in our hospital or by you in your home. There are pros and cons to each. Obviously, we're very used to taking blood and we have all the necessary equipment at the ready. We can also interpret the curve while we're taking it and adjust the frequency of sampling as needed. The downside of in-hospital glucose curves is that they can be affected by the stress of a change of routine/being in the hospital. That's where home glucose curves are most beneficial.

To create a glucose curve at home, you'll need:

  • a glucometer – there are special pet ones that claim to be calibrated for cats and dogs, but if you ever delve into the evidence regarding glucometer accuracy, you'll emerge dazed and confused. Basically, you can buy a decent glucometer from a pharmacy for somewhere between $40 and $100, look for one that doesn't cost a fortune to replace the test strips

  • fine gauge sterile needles (we can give you these)

  • cotton wool balls

Blood can be collected from the lip, ear or foot pad. 

Here's a video of taking a blood sample at home

Some people find rubbing a bit of vaseline on the ear or pad can help the blood 'bead' better. 

Once we've got a glucose curve, we can make insulin adjustments (this is an abbreviated list and we don’t recommend you go it alone with vet assistance):. 

  • If the lowest blood sugar is <4.5 mmol/L – we reduce the insulin dose by 50%

  • If the range of blood sugar levels is between 4.5 and 14 mmol/L – we keep the dose the same

  • If the peak is >14 mmol/L and the nadir is between 4.5 and 8.0 mmol/L – we either keep to the same dose and check again in 2 weeks or we increase the dose by 10% or 0.5 U/kg

  • If the peak is >14 mmol/L and the nadir is >8.0 mmol/L – Wwe increase the dose by 1-–25%

After adjusting the dose, we again stay on the new dose for 7–10 days (or more) before we make an assessment about symptom control and the need for further glucose curves/adjustments. We'll slowly adjust the dose until your dog is a controlled diabetic. Being well controlled doesn't mean that we need to achieve normal or perfect blood sugar levels.

The definition of a controlled diabetic is absence of clinical signs and no episodes of hypoglycaemia

Some dogs seem to be controlled from day one, others take weeks, even months to become controlled. Some dogs with concurrent conditions (eg Cushing’s disease) can be very difficult to control.

How is diabetes monitored?

In-clinic checkups are recommended between every 1–6 months. But the most important monitoring is done by you at home – by watching for symptoms. At home blood testing can be useful, but if it's not your thing, that's okay – just monitoring symptoms is fine. If you're wondering: 'Is there an app for that?' the answer is yes, the Royal Veterinary College (UK) has developed one! 

It is possible for controlled diabetics to become uncontrolled from time to time, for example, if other diseases such as flu or gastro occur.

What are the signs of hypogylcaemia?

The signs of low blood sugar are:

  • loss of appetite or increased hunger

  • disorientation and confusion — may show an apparent inability to complete basic routine tasks

  • weakness, low energy, loss of consciousness

  • seizures (rare)

  • anxiety, restlessness

  • tremor/shivering

If your dog shows signs of hypoglycaemia and has the ability to eat, feed her a meal. If she is unable to eat, apply some honey or sugar syrup to her gums until she is alert enough to eat her normal food. Then, feed her a meal.

If your dog is unconscious, rub a teaspoon of honey or sugar syrup on her gums. If she regains consciousness, feed her and the bring her in for a checkup. She may need to stay for observation for a while. If she remains unconscious or starts seizuring seek veterinary help immediately!

Don't give another dosage of insulin after any hypoglycemic episode until you have spoken to us (9531 1771).

The most common reason for hypoglycaemia we see is 'double dosing' of insulin, where more than one family member gives the scheduled injection. Make sure everyone knows who is responsible for insulin injections and when.