What makes blood sugar levels get low?
Carmen Patrick Mohan, MD
Internal Medicine
Hypoglycemia (low blood sugar) is uncommon in persons without diabetes. In otherwise healthy adults, fasting (lack of food) is the most common cause of low blood sugars. Medications such as insulin and drugs like alcohol are other primary culprits. Adults who are critically ill can also develop low blood sugars. In rare instances, hormonal disorders or tumors can be the problem. If for any reason you believe you are having symptoms related to low blood sugar that do not improve after eating, see a doctor for help.
Hypoglycemia occurs for a variety of different reasons. Certain medications may cause hypoglycemia like insulin taken to lower the blood sugar in people with diabetes. If you have diabetes, your eating, exercising, and medication must be carefully balanced to keep your blood sugar within the normal range. Too much exercise or not enough food, relative to your medication, can cause low blood sugar.

In people who do not have diabetes, certain medications, drinking alcoholic beverages, eating disorders, and tumors can cause hypoglycemia. Problems with your liver, kidneys, or the endocrine system may cause hypoglycemia. Sometimes hypoglycemia may occur when the body makes too much insulin in response to eating.
Michael T. Murray, ND
Naturopathic Medicine
A tendency toward hypoglycemia can be hereditary, but dietary carbohydrates usually play a central role in its cause, prevention, and treatment. Simple carbohydrates, or sugars, are quickly absorbed by the body, resulting in a rapid elevation in blood sugar level; this stimulates a corresponding excessive elevation in serum insulin levels, which can then lead to hypoglycemia. Insulin is the hormone responsible for lowering blood sugar by taking sugar out of the blood and putting it into cells. High levels of insulin mean low levels of blood glucose.
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Normal blood sugar levels, even during fasting, are usually greater than 70 milligrams per deciliter (mg/dL). Blood sugar levels that drop below normal are considered hypoglycemic, and can be caused by skipping meals, leaving too much time between meals, not eating enough, incorrect medication use (especially insulin), vomiting, diarrhea, vigorous exercise or drinking too much alcohol. While hypoglycemia can occur at any time, it is most common at night and early morning.
Your blood sugar (glucose) levels can get too low if you eat less than usual, skip meals or snacks, or eat too late, according to the National Institutes of Health. They can also get too low if you drink alcohol on an empty stomach or exercise more than usual. Some diabetes medicines may also lower your blood sugar too much. Blood sugar levels below 70 mg/dL are considered unhealthy and might cause you to feel shaky, tired, sweaty or nervous, or even to faint. Talk to your doctor for more information about low blood sugar.
William Lee Dubois
Endocrinology Diabetes & Metabolism

So here’s the deal: your body doesn’t like low blood sugar anymore than you do. In fact, when everything is working “right” low blood sugars are pretty much unheard of. Your body tries to keep your blood sugar stable using a process called homeostasis.

Homeostasis is sometimes wrongly viewed as a stable state, but in fact, it's a tremendously elegant dance. The body keeps things stable by making nearly constant small adjustments.  Picture one of those old-fashioned balance scales with the chains and the plates. Like the lady justice figures hold. Imagine you have a bag of salt. The left plate is a little low, so you put a few grains on the right. Now the left plate goes a little high. So you throw a few grains on the left plate, but you over do it, and now it heads south again. So you add more to the right….

When it comes to blood sugar, the body uses insulin from the pancreas and sugar from the liver to keep your scale's plates in balance. It your sugar goes up a bit, your body pumps some insulin into the blood to lower it again. If you sugar goes down a bit, your body releases some sugar from the liver into the blood to bring it back up.

But for the blood sugar to go low, to the point where homeostasis can’t correct it, typically requires some outside interference. The most common cause of low blood sugar is too much of a blood sugar lowering medication; or a change in the circumstances surrounding the use of the medication.

If you take too much insulin, you will go low.

If you take the right amount of insulin and then eat less than you planned, you will go low.

If you take the right amount of insulin and eat exactly what you planned but are more active than usual, you will go low.

If you take the right amount of insulin and eat exactly what you planned and are not more active than usual but drink a bunch of alcohol, you will go low.

Also, medications of the sulfonylurea class cause the pancreas to overproduce insulin independent of the homeostasis mechanism, so they can force you low if you eat less, are more active, or drink more booze than usual. These meds are pills and go under the names Glyburide, Glipizide, Glucutrol, Amaryl, and the like. Prandin and Starlix, while actually a separate class of drugs, can have the same effect.

Although less common, a wide assortment of medications that are for conditions other than diabetes can also cause low blood sugar as an unintended side effect.

Continue Learning about Hypoglycemia Causes and Risk Factors

Important: This content reflects information from various individuals and organizations and may offer alternative or opposing points of view. It should not be used for medical advice, diagnosis or treatment. As always, you should consult with your healthcare provider about your specific health needs.