The Highs and Lows of Blood Sugar
What is “blood sugar”?
Blood sugar, also referred to as blood glucose, is the main sugar found in the bloodstream of humans and animals. Glucose comes from the food eaten and is the main source of energy. The body converts carbohydrates from food into glucose, which is a simple sugar. The blood carries glucose to all the cells in the body to supply energy.
The pancreas is an organ that is positioned in the abdomen between the stomach and the intestines. Islet cells in the pancreas secrete the hormones insulin and glucagon. Both hormones work in balance to regulate blood-sugar levels. If the level of one hormone is higher or lower than the ideal range, blood sugar levels may spike or drop.
Together, insulin and glucagon help maintain a state called homeostasis, in which conditions inside the body remain steady. When blood sugar is too high, the pancreas secretes more insulin. Insulin helps the cells absorb glucose, reducing the amount of sugar in the bloodstream and providing the cells with glucose to use for energy.
When blood-sugar levels drop, the pancreas releases glucagon to raise them. Glucagon instructs the liver to convert glycogen to glucose, making glucose more available in the bloodstream. This balance helps provide sufficient energy to cells while preventing the nerve damage that can result from consistently high levels of blood sugar.
Blood-glucose levels change throughout the day. After eating, levels rise and then settle after about an hour. They are at their lowest point before the first meal of the day. The ideal range for blood sugar in humans and canines is from 80 to 130 mg/dL.
What would cause the blood-glucose level to be too low?
The medical term for abnormally low levels of sugar in the blood is “hypoglycemia.” Since glucose is the main source of energy in a human or animal’s body, a low level will result in a severe drop in energy levels, possibly to the point of unconsciousness.
Most cases of hypoglycemia are associated with diabetes and an overdose of insulin, but there are other conditions that will cause blood-sugar levels to plunge to a dangerous level. Hypoglycemia is an indication of another underlying health problem.
Puppies, especially those under the age of three months, have not fully developed their ability to regulate their blood-glucose levels. Hypoglycemia can be brought on when puppies are introduced to stress factors such as poor nutrition, cold environments and intestinal parasites. Toy and small breeds are especially susceptible to this problem.
Xylitol is a sugar alcohol that is used as a sweetening agent in many foods, candies, chewing gums, mints and supplements. It is also used as a cooling agent in nasal sprays, diapers, baby wipes, sunscreens, mouthwashes and toothpaste. Although there are many other sugar alcohols, xylitol is the only one that is dangerous to dogs.
Ingestion of xylitol can cause hypoglycemia, vomiting, depression, diarrhea and seizures. Liver failure and excess insulin release can result within 12 hours of ingestion. Consuming more than 100 mg/kg leads to abnormally low, potentially fatal blood-sugar levels. If you think your dog may have eaten gum or candy containing xylitol, see your veterinarian immediately.
Hypoglycemia can also be brought on by fasting combined with rigorous exercise and dehydration. Dogs being treated for Addison’s disease, low thyroid, liver disease, tumors of the pancreas or portosystemic shunts are at greater risk.
What are the symptoms of low blood sugar?
Dogs experiencing low blood sugar will be weak, uncoordinated and lethargic, and exhibit a “rag doll” demeanor. They may exhibit muscle twitching, trembling or blindness. In the worst cases, dogs may have seizures and lose consciousness.
These symptoms are not specific to hypoglycemia. There may be other underlying medical causes. The best way to determine hypoglycemia is by having the blood-sugar level measured while the symptoms are present.
The brain needs a steady supply of glucose to function properly, as it does not store or create glucose itself. Critically low blood-sugar levels need to be corrected quickly before irreversible brain damage or death occur.
How is hypoglycemia treated?
There are two types of treatment for low blood sugar. One treatment addresses the immediate episode to raise blood-sugar levels right away. The other treatment addresses the underlying condition in order to prevent hypoglycemia from happening again.
The initial treatment for hypoglycemia depends on the severity of the symptoms. Mild symptoms can be treated by consuming sugar orally in any form, such as honey, Karo syrup or orange juice. In more serious cases where the dog cannot take anything orally safely, your veterinarian will need to give a glucose solution intravenously. This remedies the deficiency instantly, much like watering a wilted plant.
Once your veterinarian has determined the underlying cause, a treatment plan would be determined based on the results of blood tests, urine screening, radiographs and ultrasound. The treatments could include medications, insulin dose adjustment or treatment for certain types of tumors.
Diet and management are the best ways to control hypoglycemia. Providing proper nutrition on a regular schedule is important, especially for puppies. Prevention, and being prepared to act quickly should the condition arise, are the best steps to take to ensure your dog’s health.
What would cause the blood-sugar level to be too high?
Abnormally high levels of sugar, or glucose, in the blood is called “hyperglycemia.” Unlike the opposite condition, hypoglycemia, it is not immediately life-threatening. The hormone insulin is released by the pancreas into the bloodstream when glucose levels rise, thus maintaining normal blood-sugar levels. When there is a deficiency of insulin produced or released, the blood-sugar levels remain abnormally high.
The most common reason for hyperglycemia in dogs is the disease diabetes mellitus. When the pancreas cannot produce enough insulin, either temporarily due to inflammation of the organ (pancreatitis), or permanently because of the loss of insulin-producing Islet cells, owners will need to give their dogs daily or twice-daily injections of insulin to maintain a normal level of blood sugar. At my hospital, this is usually a time of high anxiety for owners, but the insulin needles are tiny and the dogs do not react to the injection. Once a routine of feeding a meal then giving the shot is established, the vast majority of dogs do well.
Other causes for elevated levels of blood sugar are stress, drug interactions (some heartworm medication), hyperadrenocorticism (Cushing’s disease), high progesterone levels and nutritional solutions containing high amounts of glucose. Dental, kidney or urinary-tract infections can drive blood-sugar levels up, as can certain types of tumors.
How do I know if my dog has high blood sugar?
The symptoms of hyperglycemia vary depending on the underlying condition. The more common symptoms are increased thirst and urination, depression, weight loss, excessive hunger and dehydration. Many diabetic dogs develop cataracts in their eyes and nerve problems in their legs. There may be tissue damage and wounds that do not heal. Infections are hard to clear up as the excess sugar feeds invading fungus and bacteria.
Your veterinarian will determine the level of sugar in your dog’s blood and urine. Some conditions are temporary, such as stress or hormones. Other conditions will require treatment. Radiographs and ultrasounds may be needed to diagnose the underlying cause.
In the case of diabetes, commitment for treatment for the dog’s life is required. These dogs also benefit from special low-carbohydrate, high-protein, low-fat and high-fiber diets. For the best results, strict adherence to the treatment guidelines will help avoid major fluctuations in blood-sugar levels.