Hypoglycemia in Dogs: Causes, Symptoms, Treatment

Hypoglycemia in dogs (low blood sugar) can occur for a variety of reasons, and may cause anything from weakness and lethargy to seizures or a coma. Integrative veterinarian Dr. Julie Buzby discusses the causes of hypoglycemia, symptoms to watch for, what to do if you see them, and how your vet will address your dog’s hypoglycemia.

Unless you are the parent of a diabetic dog, you may not give much thought to your dog’s blood sugar on a daily basis. However, since glucose is the preferred fuel for the cells in the body, it is important that your dog’s body work hard to maintain blood glucose levels in a safe range.

If something happens to upset blood sugar regulation, blood glucose can dip too low, leading to hypoglycemia.

What is hypoglycemia in dogs?

Hypoglycemia is a medical term that refers to low levels of glucose (sugar) in the blood. Normally, a dog should have a blood glucose between 60 mg/dL to 111 mg/dL (exact numbers may vary depending on the diagnostic lab’s reference intervals).

Strictly, speaking a dog is considered hypoglycemic when blood glucose levels drop to 60 mg/dL or lower. However, for very young puppies and for diabetic dogs, some veterinarians believe having a blood glucose less than 80-90 mg/dL constitutes hypoglycemia.

What is glucose?

Glucose is a simple sugar that is the primary energy source for tissues, organs, and cells in the dog’s body. There are three main sources of glucose for dogs:

1. The dog’s diet: Digestion of dietary carbohydrates releases glucose molecules.
2. Gluconeogenesis (making new glucose): The body can create glucose from non-carbohydrate molecules in the body such as amino acids and lactate. The process of generating new glucose molecules is called gluconeogenesis.
3. Glycogenolysis (releasing stored glucose): The body can store glucose in the liver and muscles as glycogen. Then when it needs more glucose, the body breaks down glycogen to release glucose. This is called glycogenolysis.

Control of blood glucose levels

To help maintain blood glucose in the ideal range, the body relies on a balance between the hormones that increase blood glucose and those that decrease it.

When glucose levels are too high in the blood, after a meal for example, the pancreas releases the hormone insulin. It works to lower blood glucose levels by pulling glucose into cells. This allows the cells to use the glucose for energy. And the liver or muscles can also store excess glucose as glycogen.

On the other hand, in the face of low blood glucose, the body releases several hormones. One major player is the hormone glucagon, which signals the liver to undergo gluconeogenesis and glycogenolysis to raise blood glucose. Plus, the stress hormone cortisol can trigger gluconeogenesis and decreases glucose use in some tissues. Growth hormone and epinephrine also play a more indirect role in helping increase blood glucose.

What causes hypoglycemia in dogs?

The causes of hypoglycemia in dogs can generally be broken down into three categories: excessive insulin exposure, increased glucose usage, and decreased glucose production. It is important to note, though, that for some conditions, there may be more than one mechanism at play.

Hypoglycemia in dogs due to increased insulin levels

If there is too much insulin in circulation, it drives an excessive amount of glucose from the blood into cells. This results in hypoglycemia. Some potential causes include:

Insulin overdose in diabetic dogs

Diabetic dogs require daily insulin injections because their pancreas doesn’t make enough insulin to pull dietary sugar into the cells. In order to maintain the blood glucose in an acceptable range, the dog needs to eat and then receive a set amount of insulin at a set time.

If multiple dog parents give a dose of insulin because they don’t know the dog already had it, or the dog parent gives too much insulin due to a measuring error, this may cause hypoglycemia. Additionally, when your diabetic dog won’t eat, giving the normal amount of insulin may lead to low blood sugar.

Insulin-releasing tumor (insulinoma)

While uncommon, dogs can develop a functional pancreatic tumor called an insulinoma, which releases insulin into the bloodstream. The dysregulated insulin secretion can result in a critically low blood sugar. Unfortunately, these tumors are often malignant (cancerous). And in about half of cases, the insulinoma will have already spread by the time of diagnosis.

Xylitol toxicity

Excessive insulin release can also occur with birch sugar (xylitol) toxicity in dogs. This sugar substitute may be found in chewing gum, candy, medications, supplements, certain peanut butters, and many other places. Most commonly it will be listed as either xylitol or birch sugar on the label. But does have other names as well.

If a dog consumes even a tiny amount of xylitol, it quickly activates 2.5 to 7 times greater insulin secretion from the pancreas than would be expected with an equal amount of glucose. This results in dangerously low levels of blood glucose in as little as 30-60 minutes. Additionally, xylitol toxicity can cause acute liver damage.

Ingestion of diabetes medications intended for people or cats

If a dog ingests a sufficient amount of a medication for type-2 human diabetics (glipizide, metformin, etc.) or diabetic cats (bexagliflozin or velagliflozin), he or she may develop hypoglycemia.

Hypoglycemia due to increased glucose utilization

When dogs burn through more glucose than normal and the body can’t keep up with the demand, hypoglycemia may occur. Some diseases or situations that may increase glucose utilization include:

• Infections: Bacterial infections, viral infections (parvovirus or coronavirus), and protozoal infections (babesiosis) may cause increased glucose consumption.
• Sepsis: In sepsis in dogs (a dysregulated inflammatory response to infection), more glucose gets used up by the inflammatory cells and bacteria. Plus, the dog may be eating less, and the liver might not be functioning as well. This combination of factors can lead to hypoglycemia.
• Extreme exercise: Lean hunting or working dogs who exercise excessively may experience “hunting dog hypoglycemia.” However, this isn’t likely to happen in well-conditioned dogs doing routine working tasks.
• Cancer: Non-pancreatic tumors may use up glucose, secrete insulin-like molecules, and/or impair liver function. The end result is paraneoplastic (occurs alongside cancer) hypoglycemia. Some tumors on the list include:
  • Lymphoma in dogs
  • Hemangiosarcoma in dogs
  • Liver cancer in dogs (hepatocellular carcinoma, hepatoma)
  • Leiomyosarcoma/leiomyoma (smooth muscle tumors)
  • Oral melanoma in dogs
  • Lung cancer in dogs (carcinoma or adenocarcinoma)
• Reproductive conditions: Low blood sugar may occur in breeding dogs due to pregnancy, lactation, dystocia (difficult birth), or eclampsia (low calcium in nursing female dogs).
• Emergency situations: Heat stroke in dogs, prolonged seizures in dogs (status epilepticus), certain toxins (tremorgenic mycotoxins, ethylene glycol, zinc, etc.) may all cause the dog to use more glucose than normal.

Hypoglycemia due to decreased glucose production

Finally, hypoglycemia may occur when the dog isn’t able to make or mobilize enough glucose. This tends to be the cause in neonates, toy breed puppies, and dogs with liver dysfunction or endocrine diseases.

Neonatal hypoglycemia

Newborn puppies have low body fat reserves, less muscle mass, and limited glycogen stores. Plus, they have immature liver enzyme systems, making it harder for gluconeogenesis to occur. All these factors contribute to their increased susceptibility to low blood glucose levels.

Any neonate can develop hypoglycemia. But it may be more common in smaller puppies (runts), puppies who have another illness, toy breeds, those born via c-section, or those born after a difficult delivery.

Toy breed hypoglycemia

Toy breed puppies are extremely prone to hypoglycemia, both as neonates and as young puppies. If you adopt a toy breed puppy, he or she may need to eat 4-6 times a day to maintain a normal blood sugar. You may also need to feed soft food as toy breeds tend to have delayed eruption of their teeth. Plus, they may get cold easily.

Missing a meal or not having enough teeth to eat hard food, becoming cold and lethargic, fleas or other parasites, and various diseases (especially those that cause vomiting and diarrhea) can quickly tip the scales toward low blood sugar for toy breed puppies.

Liver disease

Dogs with liver dysfunction are prone to hypoglycemia from decreased glucose production. This is because the liver is one of the most important organs when it comes to glucose storage, and production. The following liver diseases in dogs may cause hypoglycemia:

• Hepatitis: Liver inflammation (hepatitis in dogs) may alter liver function.
• Liver toxicity: There are a variety of toxicologic causes of hypoglycemia in dogs. Consuming alcohol, acetaminophen, xylitol, and certain plants (death cap mushrooms, sago palm, etc.) can lead to liver damage and poor glucose regulation.
• Liver shunts: A congenital portosystemic shunt (blood vessel that causes blood from the digestive tract to bypass the liver) may also cause low blood sugar.
• Liver cancer: In addition to causing increased glucose utilization, liver cancer may impair the liver’s ability to make and release glucose.
• Glycogen storage disease: Dogs with this rare inherited disorder have defects in the enzymes that break down glycogen, making them unable to use glycogen as a source of glucose. This may lead to hypoglycemia.

Endocrine diseases

In Addison’s disease in dogs (hypoadrenocorticism), the body may not make enough of the stress hormone cortisol. This can lead to decreased gluconeogenesis and increased sensitivity to the effects of insulin. As a result, the dog may be hypoglycemic.

Growth hormone also plays a role in raising blood glucose. Thus, dogs with a growth hormone deficiency (pituitary dwarfism) may be hypoglycemic.

Poor blood sample handling

It is also worth noting that a dog can falsely appear to be hypoglycemic on blood work if the serum (fluid part of blood) is not separated from red blood cells right away. Your vet will work hard to ensure that the sample is handled correctly to avoid this. And he or she will also take any delays in separating the sample into account when interpreting the results.

What are the symptoms of hypoglycemia in dogs?

The severity of a hypoglycemic dog’s symptoms will depend on the duration and degree of the lowered glucose levels. Dogs with very mild hypoglycemia or chronic hypoglycemia might be asymptomatic. But once glucose drops below 40-50 mg/dL, clinical signs usually start to show up. (As a reminder, normal glucose is around 60-111 mg/dL and hypoglycemia is anything under 60 mg/dL).

Neurological symptoms

The brain relies on glucose to function yet cannot make or store it the way other tissues do. Thus, neurological symptoms are common in dogs with a low blood sugar. They may include:

• Weakness or unsteadiness: In mild cases, the dog may barely seem weak. More severely affected dogs may have significant trouble standing or walking. And the dog’s legs might wobble, shake, or collapse underneath him or her.
• Stumbling gait (ataxia): You might notice your dog is wobbly and off balance when walking or standing.
• Muscle tremors: The legs or the whole body might be shaking, twitching, or trembling. As the blood sugar continues to drop, the dog might begin to twitch or shake uncontrollably.
• Collapse: Your dog may be so weak, depressed, and disoriented that he or she collapses and can’t get back up again.
• Seizures: Because the brain is dependent on glucose, hypoglycemia can cause seizures. Most commonly, the dog may lose consciousness, fall over, become stiff, start paddling, drool, and/or lose bowel and bladder control.
• Blindness: The dog may be stumbling and bumping into things due to being blind.
• Coma: In extremely severe cases of hypoglycemia, the dog may be unconscious and unable to be roused.

Behavioral symptoms

In addition to the physical symptoms, you may notice some behavioral symptoms of hypoglycemia:

• Anxiety: Feeling “funny” might make the dog more anxious. This could look like pacing, panting, hiding, or clinging to a dog parent.
• Disorientation and confusion: The dog may not seem to be processing things as quickly. Or she or she may act unsure of his or her surroundings or not know what to do.
• Excessive vocalizing: Some hypoglycemia dogs bark, whine, or whimper.

Generalized symptoms

Dogs with a low blood sugar may also experience some more generalized symptoms such as:

• Lack of appetite: Low blood glucose may make your dog not feel like eating. This can worsen hypoglycemia in diabetic dogs, toy breed puppies, or neonates.
• Lethargy: Laying around more, seeming tired, or being less interactive are all indicators of a lethargic dog.
• Gastrointestinal signs: Sometimes hypoglycemic dogs may vomit and/or have diarrhea.

Hypoglycemia in dogs is an emergency

If you are seeing the signs of hypoglycemia, make an emergency vet visit immediately. Time is especially of the essence for dogs who are in a coma, having seizures, unable to stand, extremely disoriented, or tremoring significantly. However, in general, hypoglycemic dogs need prompt diagnosis and treatment for the best chances of a good outcome. Left untreated (or sometimes even with treatment), hypoglycemia can cause brain damage or death.

How will the vet diagnose a dog with hypoglycemia?

Upon arriving at the veterinary hospital or ER, the veterinary team will ask about toxin exposure, insulin overdose, health history, or other relevant pieces of information. Plus, they will be triaging your dog at the same time to determine how stable he or she is.

Glucose measurement using a glucometer

If hypoglycemia is high on the differential list, the vet may take a “dog side” glucose measurement using a glucometer. This is a hand-held device similar to the glucometers that diabetic humans may use, but it is coded specifically for dog blood. (Human glucometers are less accurate for determining blood glucose in dogs and may underestimate the glucose levels.)

Glucometers are helpful because they rapidly provide a blood glucose reading and only require a drop of blood. This allows the vet to start potentially life-saving treatment for hypoglycemia without waiting for the results of a chemistry panel. Chemistry panels also require more blood, which can be problematic in a tiny hypoglycemia toy breed puppy.

On the flip side, glucometers are generally considered to be less accurate at determining blood glucose than biochemistry analyzers (what the vet clinic or reference lab uses to run blood tests). They can also be skewed by a low or high red blood cell concentration in the blood.

Chemistry profile and CBC

The vet will likely also run some blood tests for dogs, including a blood chemistry profile and complete blood count (CBC). This allows him or her to have a more accurate measure of blood glucose. Plus, the vet can detect high liver enzymes in dogs, look for indicators of liver dysfunction or signs of infection, and gather more information about the dog’s overall health status.

Additional diagnostics

Depending on the dog’s symptoms, history, and exam and blood work findings, the vet may recommend additional diagnostics to track down the cause of the hypoglycemia. This could involve specialized blood work such as measuring paired glucose and insulin levels to look for an insulinoma or running an ACTH stimulation test to diagnose Addison’s disease. Additionally, imaging such as X-rays or ultrasounds may be helpful for detecting masses, organ enlargement, etc.

Continuously monitoring glucose levels while hospitalized

Some veterinarians will use continuous glucose monitoring (CGM) equipment like FreeStyle Libre devices to track glucose levels in hospitalized patients. Others may take frequent glucose measurements using the glucometer. In either situation, the goal is to carefully track the dog’s blood glucose during treatment and adjust the plan accordingly.

How is hypoglycemia treated in dogs?

Treatment of hypoglycemia involves bringing the blood glucose back up into a safe range and addressing the underlying cause of the low blood sugar.

IV dextrose (glucose) supplementation

The best treatment for symptomatic hypoglycemia is administering glucose in the form of a diluted dextrose solution directly into a vein. Often, the dog’s symptoms will improve within minutes of starting the IV dextrose. If continued glucose support is needed, such as in cases of insulin overdose, the vet may put the dog on a continuous rate infusion (CRI) of dextrose.

Glucagon infusions

If the dog received an insulin overdose, has an insulinoma or tumor secreting insulin-like molecules, or isn’t responding well to dextrose, the vet may try a glucagon CRI instead. (Remember, glucagon is the hormone that stimulates glycogenolysis and gluconeogenesis to raise blood glucose.)

Addressing the underlying cause

Hypoglycemic dogs may need emergency care not only for the hypoglycemia, but also for the heat stroke, toxin ingestion, sepsis, seizures, or whatever it was that triggered the hypoglycemia. And it will also be important to address less urgent problems such as cancer or liver disease. The vet will work with you to formulate a plan that is right for your dog.

Can you treat hypoglycemia in dogs at home?

Home treatment is best reserved for very mild hypoglycemia (for example in a toy breed puppy who didn’t eat as well as normal and could be at risk for low blood sugar). And it serves as a way to help raise blood glucose on the way to the emergency vet.

Applying a sugary substance to the gums (then heading to the vet in many cases)

If you can do it safely, it can be helpful to rub some honey, maple syrup, or Karo syrup on a hypoglycemic dog’s gums. (Important note: Be sure you are not using an imitation or sugar-free product that may contain the toxic sugar substitute xylitol.) Or, if you have it on hand and your dog is alert and swallowing, you can offer your dog a high calorie supplement like Nutri-Cal®.

These methods of glucose supplementation have value. But they are not a substitute for veterinary care if your dog is weak, vomiting, seizing, mentally depressed, comatose, or showing other significant signs of hypoglycemia.

If there is any doubt in your mind about your dog’s status, you should head to the vet. It’s much better to get there and find out that the sugar has perked your dog up again than to waste valuable time at home hoping your dog will improve. Remember too, there are plenty of situations where the hypoglycemia AND the cause of the hypoglycemia require emergency care.

Addressing hypoglycemia in diabetic dogs at home

If you have a diabetic dog, your vet will most likely give you an action plan for hypoglycemic events. In some cases of mild hypoglycemia (as indicated by glucometer or CGM readings), the vet may have you feed your dog a small meal if he or she is otherwise stable and not vomiting. Or the vet may want you to rub honey, maple syrup, or Karo syrup on the gums.

More severe hypoglycemic episodes or insulin overdoses generally require emergency veterinary care, though.

Managing hypoglycemia in toy breed puppies at home

Since toy breed puppies are particularly sensitive to hypoglycemia, it will be important to carefully monitor their behavior and food intake. Plus, they should not go a long time without food. Having something like Nutri-Cal on hand can be a good way to give your tiny puppy a concentrated source of sugar and energy if he or she seems a bit off or doesn’t eat well. However, your vet can advise you more specifically about the precautions you should take for your puppy’s situation.

In the event that your toy breed puppy is also vomiting, having diarrhea, acting weak and lethargic, or doesn’t quickly respond to the meal or Nutri-cal, it is important to promptly seek veterinary care. These little puppies don’t have many reserves.

What is the prognosis for hypoglycemia in dogs?

The prognosis varies greatly depending on the severity and cause of the hypoglycemia and the dog’s response to treatment. A toy breed puppy with mild hypoglycemia after skipping a meal or two may bounce back and be just fine. However, hypoglycemia due to toxins like xylitol can rapidly become fatal. And the prognosis can be poor for some dogs with cancer, heat stroke, or sepsis.

Overall, dogs who have a rapid resolution of their symptoms with treatment tend to have a better prognosis. But still, in one study of 255 hypoglycemic dogs who came through the emergency department, there was a 65% mortality (death) rate for dogs with severe hypoglycemia.

Your veterinarian can help you understand what your dog’s prognosis looks like based on the cause and severity of the low blood sugar and how your dog is doing after treatment.

How can you prevent hypoglycemia in dogs?

It isn’t possible to prevent all emergency situations, but there are a few steps you can take that may reduce the risk of your dog developing hypoglycemia.

1. If you have a diabetic dog and share insulin administration duties with another person in your home, be sure to have ways to clearly communicate when insulin was given to your dog. And if your diabetic pup isn’t eating, don’t give insulin. Instead, call your veterinarian.
2. Keep artificial sweeteners out of reach of your dog. And check the ingredient labels on any food items or supplements you give your dog to ensure they don’t contain xylitol (birch sugar). If you suspect that your dog ingested something containing xylitol, contact animal poison control right away. And be prepared to head to the emergency vet.
3. Bring your dog to the vet for routine wellness appointments and screening blood work. This may allow your vet to catch some of the conditions that cause hypoglycemia before they become a big problem.
4. Frequently feed toy breed puppies an easy-to-eat, high calorie food and monitor them closely for signs of hypoglycemia.

When it comes to hypoglycemia, time is of the essence

If your dog is showing clear signs of hypoglycemia or is at high risk for hypoglycemia due to toxin ingestion, heat stroke, or other conditions, it is critical that you seek veterinary care as soon as possible. Apply some honey, maple syrup, or Karo syrup to your dogs gums and then head to the vet. The sooner your dog gets the care he or she needs, the better the prognosis tends to be.

Has your dog ever experienced a hypoglycemic event?

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