What is hypoglycemia?

The symptoms of hypoglycemia are a good warning sign; being unaware of falling blood glucose levels can cause serious problems.


A low blood glucose level triggers the release of epinephrine (adrenaline), the “fight-or-flight” hormone. That’s why a low can cause a thumping heart, sweating, tingling, and anxiety.

If the blood glucose level continues to drop, the brain does not get enough glucose and stops functioning as it should. This can lead to blurred vision, difficulty concentrating, confused thinking, slurred speech, numbness, and drowsiness. Prolonged starvation of the brain may lead to seizures, coma, and very rarely death.

Hypoglycemia Unawareness

The symptoms of hypoglycemia are a good warning sign; being unaware of falling blood glucose levels can cause serious problems.

However, some people don’t get these early symptoms. If hypoglycemia occurs too frequently, the body gets used to hypoglycemia and stops sending out the adrenaline alert every time blood glucose dips too low. This is called hypoglycemia unawareness. The first symptoms are the ones that occur when the brain is not getting enough glucose.

Hypoglycemia unawareness puts the person at increased risk of severe low blood glucose reactions (when a person may pass out or have a seizure). People with hypoglycemia unawareness need to take extra care to check blood glucose frequently, particularly prior to and during critical tasks such as driving. A continuous glucose monitor can be a huge help, which can sound an alarm for a falling as well as a low blood glucose level.

Causes of Lows

Hypoglycemia is common; the average person with type 1 diabetes experiences an estimated two episodes of mild hypoglycemia each week, and that’s only counting those episodes with symptoms. Adding in asymptomatic and overnight hypoglycemic events would likely drive that number up.

Almost all lows have a cause, although sometimes it is hard to figure out exactly why they happened.


Too much insulin is a sure route to hypoglycemia. One reason newer insulins are preferred over NPH and regular insulin is that they’re less likely to cause blood glucose lows, particularly overnight. Insulin pumps may also reduce the risk of hypoglycemia. Accidentally injecting the wrong insulin type or an excessive dose of insulin or injecting directly into the muscle, instead of the subcutaneous tissue, can cause hypoglycemia.


Eating foods with less carbohydrates than usual may lead to hypoglycemia if insulin isn’t lowered to compensate. How much of your caloric intake comes from liquids versus solids can also affect blood glucose levels. Liquids are absorbed much faster than solids, so timing the insulin dose to the absorption of glucose from foods can be tricky. The composition of the meal—how much fat, protein, and fiber are present—can affect the absorption of carbohydrates.

Physical Activity

Exercise has many benefits.The tricky thing for people with type 1 diabetes is that it can lower blood glucose in both the short- and long-term. Nearly half of children in a type 1 diabetes study who exercised an hour during the day experienced a low blood glucose reaction overnight.The intensity, duration, and timing of exercise can all affect the risk of going low.