My 29 year old boyfriend, recently diagnosed with type 1 diabetes, had low blood sugar symptoms (shaky hands, etc.), but his blood sugar level was 93 mg/dl [5.2 mmol/L]. He thought it was still high, so he did not do eat or drink anything. Two hours later, he checked his blood again and it was 140 mg/dl [7.8 mmol/L]. Why does blood sugar increase even though he does not eat anything? It also happens in the morning (e.g., before bedtime, it will be 80 mg/dl [4.4 mmol/L], then 150 mg/dl [8.3 mmol/L] the next morning).

This is a frequently asked question. The quick answer is that the liver is capable of exporting glucose from polymers of glucose called glycogen that are stored in the liver. In addition, metabolic intermediates can be taken up by the liver and turned back into glucose. One of the metabolic abnormalities that occurs in diabetes is that there is not an appropriate limit on the amount of glucose exported by the liver. It is the glucose put out by the liver that raises the blood sugar, even though a person does not eat any additional food.

Symptoms of hypoglycemia may occur if there has been a dramatic fall in blood sugar, even though the sugar is not absolutely in the low range. The body anticipates the fall and stimulates the liver to put out more glucose to protect it. Symptoms of hypoglycemia occur when the hormones, such as adrenalin, are stimulated (fast heart rate, hunger, shaking, sweating, etc.).

JTL