Backcountry health & safety

Hypoglycemia (insulin reaction)

by Susan Bradford, Ph.D., Richard Fantozzi, M.D., and Bill Fantozzi, Wilderness Remote and ER Instructor

Hypoglycemia (or low blood sugar) may be experienced during strenuous physical activities such as mountain climbing and hiking. It is certainly plausible for victims of AMS to also experience hypoglycemia, especially if they experience loss of appetite. Even at sea level intense physical activities can readily deplete a person’s blood sugar level.

Diabetics are at particular risk for hypoglycemia. Hypoglycemia in type 1 and 2 diabetics is a result of an insulin reaction, from taking too much insulin (8). There is an increasing population of undiagnosed diabetic individuals whose participation in strenuous activities may result in hypoglycemia.

Non-diabetics can also experience hypoglycemia, especially if they have missed meals or have not properly prepared before exercising. Environmental factors such as temperature affect glucose metabolism. The human body needs greater amounts of glucose when hiking, especially in temperatures below 50F (9).

Understanding the physiology

The brain is largely made up of neurons, electrically excitable cells that are responsible for our ability to think, feel, move and breathe). Neurons use glucose–the form of sugar that travels in our bloodstreams–as their energy source. Because neurons cannot make or store glucose, they rely on the bloodstream to deliver a constant supply of glucose. By definition, hypoglycemia is any level of blood glucose below 70 mg/dL. Most healthy adults develop symptoms of hypoglycemia when their glucose falls below 55mg/dl (7, 10).


Symptoms of hypoglycemia can be divided into two groups; adrenergic and neuroglycopenic (10). Adrenergic symptoms are related to the nervous system and include dizziness, hunger, sweating, shakiness and anxiety.

Neuroglycopenic symptoms include confusion, seizure and coma (10) (and generally occur when blood sugar levels fall below 50mg/dl).

Unless a person carries a glucose test kit, the only way to determine if a victim has hypoglycemia is by evaluation of their symptoms. Even so, underlying medical conditions and medications can add a level of complexity. If possible, test blood sugar levels (7). Most type 1 and 2 diabetics carry a small blood sugar test kit.


Treatment for hypoglycemia includes the rapid delivery of easily absorbed sugar into the victim. Symptoms of hypoglycemia are resolved as blood sugar concentrations return to the normal range of 70 to 100 mg/dl (8).

A general rule of thumb is to provide 15g of glucose to the victim (8). What does 15g of glucose look like? Examples include 4 lifesavers, 3 to 4 glucose tablets, one tablespoon sugar or ½ of a can of soda.

After giving the victim glucose, evaluate their symptoms (8, 10). If symptoms persist repeat with an additional 10-15g of sugar. After symptoms have been resolved, it is desirable to have a meal containing complex carbohydrates to help maintain normal blood sugar levels (10).

If a diabetic person is unable to take sugar by mouth then one may have to administer a glucagon injection (10), which diabetics should carry, especially during strenuous wilderness activities.

Never administer insulin to a diabetic victim!


Whether one is diabetic or not, prevention of hypoglycemia through proper nutrition prior to physical activity is essential. A well-balanced diet helps normalize blood sugar levels. Usually a regimen moderate in protein, unrefined carbohydrates (such as whole-grain products and vegetables, which are slow to be absorbed), and fats is recommended. Foods high in rapidly absorbed (simple) sugars should be avoided.

Alcohol, caffeine, tobacco, and other stimulants should be avoided.

Carrying glucose supplements is important while participating in any wilderness activities.


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San Diego, California