Blood Sugar Levels in Dogs: What Every Dog Owner Needs to Know

If your dog has been diagnosed with diabetes, or if you’ve set out on the journey to understand how carbohydrate restriction, ketogenic diets, and other metabolic therapies can improve your dog’s overall health and well-being, then you have likely encountered the term “blood sugar.” 

The term refers to a kind of metabolic substrate that plays several vital roles in your dog’s bodily functioning. So understanding what blood sugar is and how it is used within the body is absolutely crucial to being a smart, responsible custodian of your pup’s health and wellbeing.

But don’t worry, because you don’t need a graduate degree in animal nutrition in order to understand the key information. In fact, we wrote this article to tell you everything you need to know in one fell swoop. Let’s get started.

What Is Blood Sugar?

If someone asks you what your dog’s blood sugar level is, they’re essentially asking you how much of a substance called glucose is circulating in your dog’s bloodstream at any given time. In other words, “blood glucose” and “blood sugar” are two different ways of saying the same thing. 

Glucose is a very simple kind of carbohydrate molecule. In fact, it’s the building block of all carbohydrates. What we call “complex carbs” are those that are composed of long, intricate chains of glucose molecules. While “simple” carbs are composed of just a few. But, fundamentally, all carbs are made up of glucose molecules arranged in one way or another.

It’s key to understand that blood sugar levels are rarely stable. They tend to fluctuate significantly in response to all kinds of different stimuli. If, at any point, your dog has “high” blood sugar that just means that there’s lots of glucose in the bloodstream at that particular time, while “low” blood sugar means there’s relatively little glucose in the blood at that point.

Where Does Blood Glucose Come From?

Glucose is quite literally the stuff of life. It is the single most important source of metabolic fuel in all organisms, not just dogs. Without glucose, plants wouldn’t grow and snakes wouldn’t slither, and dogs wouldn’t play around and bark and poop in the living room. 

A helpful analogy is to think of your dog’s body as a city, with each vital organ being a different building that’s important for the city to function. In this analogy, your dog’s circulatory system is like the city’s network of roads and highways and glucose is one of the many different kinds of cars on the roads. These cars drive around on the roads until they are needed at one building or another, whereupon they cruise over to the relevant building and go inside to do whatever work needs to be done.

The glucose in your dog’s blood comes from two different kinds of sources. The first are called “exogenous” sources, meaning those originating outside of the body. By far the most common exogenous source of glucose is – you guessed it – food! More specifically, dietary carbohydrates. Recall that carbs are made up of chains of glucose molecules. So when your dog eats a carbohydrate-rich meal, she is ingesting a whole bunch of lengthy glucose chains. Those chains get broken down into individual glucose molecules during digestion, which then get absorbed into the bloodstream, causing blood sugar levels to rise.

But blood sugar can also come from “endogenous” sources, meaning those originating inside of the body. Through highly-evolved metabolic wizardry, your dog’s body can actually make glucose out of other kinds of molecules. In this regard, the most important kinds of molecules are proteins, which under certain conditions get converted into glucose through an intricate bodily process called gluconeogenesis. In the absence of dietary carbs (if your dog consumes an all-meat diet), a healthy dog will produce all of the glucose it needs from gluconeogenesis and other internal bodily processes – which is why carbs are not considered essential nutrients for dogs.

Function and Dysfunction in Blood Glucose

So if glucose is a key source of metabolic energy, is it optimal for your dog to have an abundance of it in the blood all the time?

No. In fact, if blood glucose levels get too high it is not just bad for your dog’s health but acutely toxic. If blood sugar levels get too high, your dog will suffer seizures, slip into a coma, and eventually die. In high quantities, glucose is quite literally a deadly poison.

Okay, so if too much glucose is bad for your dog, is it optimal for your dog to have none of it in the blood at all?

Also no. Having too little glucose in the blood is also deadly. When blood sugar levels get perilously low dogs don’t have enough metabolic fuel in the body to do the things they need to do to stay alive (keep their hearts pumping, keep their brains functioning, etc.).

This means that your dog’s body has to be really, really good at keeping blood glucose levels balanced within a pretty narrow range. And, fortunately, it is! The primary “tool” that is used to keep blood sugar at healthy levels is a hormone called insulin. 

Insulin is made by the pancreas and its primary function is to drive glucose out of the blood and into other tissues (like fat cells and muscles), where the glucose can be stored safely in a non-toxic form. Essentially, when blood sugar levels get too high, the pancreas notices and begins secreting more and more insulin, until the blood glucose levels come back down again. Phew, crisis averted.

At least if your dog is healthy. If, on the other hand, the animal is diabetic, then her pancreas do not produce insulin effectively enough. As a result, if your dog has diabetes, there’s often not enough insulin being produced to bring blood sugar back down to tolerable levels. So when blood sugar levels get too high (like after a carbohydrate-rich meal) they stay too high. And that can cause big-time health problems, as explained above.

This is why one of the main treatments for canine diabetes is giving your dog injections of insulin. These supplement whatever amount of insulin the pancreas can make endogenously, helping to bring blood sugar levels back down to earth.

What are “Normal” or “Healthy” Blood Glucose Levels for Dogs?

According to the American Animal Hospital Association, the “normal” range of blood glucose levels for a healthy dog is 80-200 mg/dl. As such, by the AAHA’s definition, a blood sugar level below 80 mg/dl is considered “too low” (the technical term is hypoglycemia) and a level about 200 mg/dl is considered “too high” (the technical term is hyperglycemia in dogs).

That said, healthy dogs that don’t consume much dietary carbohydrate at all rarely have blood glucose levels above 100 mg/dl. On the other hand, dogs with untreated diabetes may have blood glucose levels that are much higher than this. If you are concerned about your dog's blood glucose levels, please consult with your veterinarian.

Blood Glucose Curves for Dogs

Knowing whether your dog’s blood glucose is relatively high or low is important. But because blood sugar levels are constantly in flux, understanding levels at individual points in time isn’t all that helpful. Enter the blood glucose curve. A glucose curve is a tool used by veterinarians to monitor blood glucose levels in dogs over a period of time, usually over 12 to 24 hours. This information can be helpful in managing conditions such as diabetes, and also in diagnosing other illnesses that affect blood glucose levels.

When creating a glucose curve, a veterinarian will take blood samples at specific intervals, (usually every 1-2 hours) and measure the glucose levels in each sample. This produces a graph that shows how the dog's blood glucose levels change over time.

Here is an example of a glucose curve for a diabetic dog:

Image credit: https://www.merck-animal-health-usa.com/vetsulin/dogs/glucose-curves

In this graph, the y-axis represents the dog's blood glucose level in milligrams per deciliter (mg/dL), while the x-axis represents time in hours. The blue line represents the blood glucose level over time, while the black dots represent the times at which blood samples were taken.

Ideally, the blood glucose level should remain relatively stable throughout the day, with small fluctuations around the target range. In this example, the target range is between 100-250 mg/dL because the animal is diabetic. An ideal glucose curve for a healthy dog has a nadir (low point) of 80-150 mg/dL of blood. The curve should remain within this range for most of the day, with spikes and dips in glucose levels minimized.

Overall, glucose curves are an important tool for managing diabetes and other conditions that affect blood glucose levels in dogs, and can provide valuable information for veterinarians in helping to maintain the health of their patients.

How to Know What Your Dog’s Blood Sugar Levels Are At Any Given Point

At present, there are a few different ways to measure and monitor glucose levels in dogs.

The most common one is to draw a small amount of blood and then apply it to a testing strip in a device called a glucometer. A small needle is used to prick the skin on the paw or the inside of the ear, producing a droplet of blood. A small strip of paper is used to soak up the blood droplet, then the paper gets inserted into the glucometer. Glucometers use a chemical reaction to determine how much glucose is in the droplet and then communicate the results through some kind of monitor.

Glucometers are reliable and widely used but they aren’t without their shortcomings. The main problems are twofold: (1) they require painful skin pricks and (2) they’re pretty annoying and labor-intensive for pet owners.

As such, new technologies called “continuous glucose monitors” (CGMs) are now being used in human beings and are just on the cusp of being used with widely canine populations too. These devices live on the body and measure blood sugar levels automatically, all throughout the day. And they do it painlessly, without having to stick your dog with any needles.  See this article for more on CGMs.

Regulating Blood Glucose

Regulating blood glucose levels in dogs can be a complex process, and it is important to work closely with a veterinarian to develop an appropriate treatment plan. Here are some general guidelines for managing blood glucose levels in dogs:

• Insulin therapy: Dogs with diabetes typically require insulin injections to help regulate their blood glucose levels. The type of insulin and dosage will vary depending on the dog's individual needs and may need to be adjusted over time.
• Diet: All else being equal, low-carbohydrate diets have been shown to produce smaller blood sugar spikes than higher-carbohydrate ones (this is where Ketona comes in).
• Exercise: Regular exercise can help regulate blood glucose levels in dogs, but it is important to avoid overexertion and to monitor blood glucose levels before and after exercise.
• Medications: In some cases, additional medications may be necessary to help regulate blood glucose levels in dogs. These may include drugs that stimulate insulin production or medications that help reduce insulin resistance.
• Management of underlying conditions: Some underlying conditions, such as Cushing's disease or pancreatitis, can affect blood glucose levels in dogs. Proper management of these conditions can help regulate blood glucose levels.

It is important to work closely with a veterinarian to develop an individualized treatment plan for managing blood glucose levels in dogs. With proper management, many dogs with diabetes are able to lead happy, healthy lives.

Insulin Administration for Dogs

Insulin injections are an important part of managing diabetes in dogs. Here are some general guidelines for administering insulin to dogs:

• Insulin Type: There are different types of insulin available for dogs, including short-acting, intermediate-acting, and long-acting insulin. Your veterinarian will determine the appropriate type of insulin based on your dog's individual needs.
• Insulin Dose and Timing: The dose and timing of insulin administration will vary depending on the individual dog's needs. Your veterinarian will provide specific instructions on how much insulin to give and when to give it. Insulin is typically administered twice a day, with meals.
• Giving Insulin Injections: Typically an insulin injection is administered under the skin using a syringe. Your veterinarian or a veterinary technician should demonstrate how to properly and safely administer insulin doses to your dog.
• Site of injection: The recommended site for insulin injections is typically the scruff of the neck (between the shoulder blades) or the flank area. Your veterinarian can provide specific instructions on the best site for your dog.
• Monitoring: It is important to monitor your dog's blood glucose levels regularly, as well as to watch for signs of hypoglycemia (low blood glucose levels) or hyperglycemia (high blood glucose levels). Contact your veterinarian if you notice any concerning changes in your dog's behavior or symptoms, as both hyperglycemia and hypoglycemia can, in severe cases, be life-threatening.
• Storage: The insulin bottle should be stored in the refrigerator, and should be gently mixed before each use. Do not use the insulin that has been frozen or left out in the sun for a long period of time, or that has expired.

It is important to work closely with a veterinarian to determine the appropriate insulin dosage and administration schedule for your dog, as well as to monitor blood glucose levels regularly. With proper management, many dogs with diabetes are able to lead happy, healthy lives.