A dog with low blood sugar usually looks weak, shaky or "not there". It may tremble, wobble when it walks, act confused or sleepy, and in severe cases it can have a seizure or collapse. If you see these signs in a toy-breed puppy, a diabetic dog on insulin, or a dog that may have eaten something sugar-free, call your veterinarian or an emergency clinic now.
Hypoglycemia is not a disease on its own. It is a sign that something else is pulling blood sugar down: a puppy that went too long without food, too much insulin, a toxin, a tumor or a serious infection (Clinician's Brief). The cause decides what your vet does next.
What Is Hypoglycemia in Dogs?
The word breaks down into hypo (low) + glyc (glucose, sugar) + emia (in the blood): low blood sugar. Glucose is the body's main fuel. Between meals the liver keeps the level steady by releasing stored glucose (glycogen) and making new glucose, so hypoglycemia means sugar is leaving the blood faster than the body can replace it.
In dogs, blood sugar normally sits roughly between 70 and 120 mg/dL (labs use slightly different ranges). Low blood sugar becomes clinically important below about 60 mg/dL (3.3 mmol/L), and that is where signs become likely (Clinician's Brief). The brain depends mainly on glucose for energy, which is why most signs are neurological (Merck Veterinary Manual).
Age matters. In young puppies, mainly toy breeds, a missed meal can be enough. In adult dogs there is almost always a cause behind it: skipping a meal does not drop blood sugar in a healthy adult (Clinician's Brief), so a grown dog with low blood sugar needs a vet to find out why.
Hypoglycemia Symptoms in Dogs
How a dog looks depends on how low its blood sugar falls and for how long. Signs often come and go, and they don't always follow the order below: a dog can go straight to a seizure. Dogs whose blood sugar has been low for a long time, for example with a slow-growing tumor, can show surprisingly few signs (Clinician's Brief; Merck Veterinary Manual).
Early signs
These come from the body's alarm response as it tries to raise blood sugar:
- Trembling or shivering
- Restlessness or anxiety
- Hunger or food seeking
- Nausea or vomiting
- A fast heartbeat
Worsening signs
As the brain runs short of fuel:
- Weakness, including weak or wobbly back legs
- Stumbling or lack of coordination
- Confusion, strange behavior or seeming not to see properly
- Lethargy and unusual sleepiness
- Muscle twitching
Severe signs: an emergency
- Seizures
- Collapse or a fainting-like episode
- Not responding to you, or coma
Severe or prolonged low blood sugar can be fatal.
One thing that is not on the list: drinking and peeing a lot. Those point to high blood sugar, as in diabetes (Morris Animal Foundation).
What Causes Low Blood Sugar in Dogs?
Four situations come up again and again for dog owners, and each one changes what you tell your vet.
Toy-breed puppies
Toy-breed puppies can develop low blood sugar in roughly their first six months, while the liver is still immature. A missed or late meal is the most common trigger (Merck Veterinary Manual; Clinician's Brief). Small puppies also lose body heat quickly, and a chilled puppy eats less, which makes things worse (Metropolitan Veterinary Associates). Most puppies outgrow it as they mature.
A puppy that keeps having episodes may have a portosystemic shunt, a blood vessel that lets blood bypass the liver, which your vet can test for.
Diabetic dogs on insulin
Too much insulin is behind most cases of insulin-driven low blood sugar in dogs, usually from an accidental extra or wrong dose (Clinician's Brief). A dog that skips a meal or vomits around its insulin dose is also at risk, which is why the AAHA guidelines tell owners to contact the vet if a diabetic dog doesn't eat.
If you see weakness, lack of coordination, seizures or collapse after giving insulin, call your veterinarian immediately (Merck Veterinary Manual). Never change the insulin dose, its timing or your dog's meals without your vet's advice. If your dog is diabetic, also know the signs of the opposite emergency, diabetic ketoacidosis.
Xylitol
Xylitol is a sweetener found in sugar-free gum, candy and baked goods, and in some toothpastes and liquid medicines. In dogs, and not in cats, it triggers a sudden rush of insulin that can drop blood sugar sharply (Merck Veterinary Manual).
Signs can start within 30 minutes or be delayed by up to 12 to 18 hours, especially with gum, and some dogs develop serious liver damage a day or two later. A dog that ate xylitol and seems fine still needs a call right away: your vet, an emergency clinic or the ASPCA Animal Poison Control Center at (888) 426-4435 (open 24/7; a fee may apply). Don't try to make your dog vomit unless a vet tells you to. More in our guide to xylitol toxicity in dogs.
Insulinoma
An insulinoma is a tumor of the insulin-making cells in the pancreas that keeps releasing insulin even when blood sugar is already low. It is most common in dogs about 5 to 12 years old (Merck Veterinary Manual).
The signs come in episodes: weakness (often in the back legs), tiredness after exercise, twitching, wobbliness, confusion, collapse or seizures. Exercise, fasting or even eating can set them off, and they tend to get more frequent and longer over time. Because the signs look like a brain problem, insulinoma can be mistaken for epilepsy, and the Merck Veterinary Manual advises checking blood glucose in every older dog with episodes of weakness, collapse or seizures (Merck Veterinary Manual).
Other causes
Less often, the cause is one of these (Clinician's Brief; Morris Animal Foundation):
- Severe liver disease or liver failure
- Other tumors, such as large liver tumors and smooth-muscle tumors of the gut or spleen (Merck Veterinary Manual)
- Addison's disease (hypoadrenocorticism), where low cortisol can cause severe low blood sugar (Merck Veterinary Manual)
- Severe infection and sepsis, where low blood sugar marks a more serious case
- Long, hard work in hunting and working dogs ("hunting dog hypoglycemia")
- Starvation or severe malnutrition
- Some infections and poisons, such as babesiosis and antifreeze (ethylene glycol)
- Rare conditions: inherited glycogen storage diseases, growth hormone deficiency (pituitary dwarfism), some blood cancers, and pregnancy
What to Do If You Think Your Dog Has Low Blood Sugar
Call your veterinarian or the nearest emergency clinic now and say you suspect low blood sugar. The vet may tell you over the phone how to raise your dog's sugar before you arrive (Merck Veterinary Manual).
If your dog is on insulin, the AAHA diabetes guidelines teach owners to rub corn syrup on the gums and then take the dog to a vet, and they warn that a drowsy dog can inhale it. If your vet has shown you this, do it only while you call or drive. Never pour liquid into your dog's mouth, and put nothing in the mouth of a dog that is seizing or unresponsive. Keep your fingers clear, because a confused dog may bite (Clinician's Brief).
On the way, keep your dog warm and quiet. Bring the insulin bottle, any packaging your dog chewed, or a quick note of what happened and when.
Call now
- Seizure, collapse, or your dog won't respond to you
- Trembling, weakness, wobbling or confusion in a toy-breed puppy
- Any of these signs in a diabetic dog on insulin
- Your dog ate anything containing xylitol, even if it seems fine
See your vet soon
- An older dog with episodes of weakness, wobbliness, odd behavior or collapse that pass on their own. Ask about a blood sugar check.
- A puppy or dog that has had one episode and recovered. The cause still needs finding.
How Vets Diagnose and Treat Hypoglycemia
The first step is a quick blood glucose test, often with a handheld meter and a drop of blood. A sample that sits too long before testing can read falsely low, so the vet may recheck a low result (Morris Animal Foundation; Clinician's Brief).
Treatment starts by bringing the blood sugar back up: with food by mouth if the dog is alert, or with glucose given into a vein if it is not. Your veterinarian chooses the method and amount. Dogs that ate xylitol or got too much insulin may need to stay in the hospital with repeated sugar checks, because their blood sugar can drop again (Merck Veterinary Manual).
Then the vet looks for the cause. Depending on your dog's age and history, that can include:
- Bloodwork and urine tests for liver disease, infection and Addison's disease
- A blood insulin level measured at the same time as a low glucose, to look for an insulinoma
- Imaging of the abdomen. CT is the preferred scan for insulinomas, because ultrasound misses many of them (Merck Veterinary Manual)
What comes after depends on the cause: a feeding plan for a toy puppy, an adjusted insulin plan, treatment for liver or adrenal disease, or surgery and medication for an insulinoma.
Outlook
The outlook depends on the cause and how fast treatment starts. Toy puppies usually do well once their feeding is sorted out, and most outgrow the problem. Xylitol cases without liver damage have a good outlook when treated promptly; severe liver damage is more serious (Merck Veterinary Manual). Insulinomas are often malignant, but removing the tumors can control the signs, and some dogs live well for more than a year, sometimes over two years (Merck Veterinary Manual).
Whatever the cause, repeated, long or severe episodes of low blood sugar can cause lasting brain damage (Merck Veterinary Manual). That is the main reason not to wait.
Lowering the Risk
Toy-breed puppies need frequent meals of a commercial puppy food on the schedule your vet recommends, and they need to stay warm. Diabetic dogs do best when the insulin and meal plan never changes without the vet: never guess a dose, and ask whether home glucose checks make sense for your dog. Keep gum, mints, sugar-free treats and toothpaste out of reach, and read the label of anything marked "sugar-free" before sharing it. If you have a hunting or working dog, ask your vet how to fuel it for long, hard days.
For any dog, note what was happening before an episode (fasting, exercise, a recent meal or insulin dose) and tell your vet. It helps them find the cause.
Originally written by Akosua Kumi Nyarko. Updated by the I Love Veterinary editorial team.
Sources
- Merck Veterinary Manual: Disorders of the Pancreas in Dogs
- Merck Veterinary Manual: Islet Cell Tumors in Dogs and Cats
- Merck Veterinary Manual: Xylitol Toxicosis in Dogs
- Merck Veterinary Manual: Congenital and Inherited Cerebral Disorders in Small Animals (Puppy Hypoglycemia)
- Merck Veterinary Manual: Addison Disease (Hypoadrenocorticism) in Animals
- Merck Veterinary Manual: Endocrinological Paraneoplastic Syndromes in Small Animals
- AAHA: 2018 AAHA Diabetes Management Guidelines for Dogs and Cats
- Clinician's Brief: Hypoglycemia (Thomas Schermerhorn, VMD, DACVIM)
- Morris Animal Foundation: Sugar Highs and Lows, What You Need to Know About Blood Glucose
- Metropolitan Veterinary Associates: Hypoglycemia in Small Breed Puppies and Young Kittens
- ASPCA Animal Poison Control Center
This article is for general information and is not a substitute for advice from your veterinarian.
