Hypoglycemia

What Is It, Causes, Testing, Treatment, and More

Author: Ahaana Singh

Editors: Antonella Melani, MD, Lisa Miklush, PhD, RN, CNS

Illustrator: Meg Gullotto


What is hypoglycemia?

Hypoglycemia is the medical term used when blood glucose levels drop below what is considered to be healthy (below 70 mg/dL in adults). As glucose is one of the main sources of energy for the body, hypoglycemia can be dangerous. Glucose is a sugar that is typically obtained from consuming carbohydrates, such as bread or fruit. After a meal, glucose gets absorbed from the gut into the blood. In order to use this glucose, the body produces insulin, which is a hormone that helps cells absorb glucose from the blood. 

What does hypoglycemia mean?

Hypoglycemia literally refers to low blood glucose levels: the prefix “hypo” means “below,” while “glycemia” means “glucose in blood.”

What are the signs and symptoms of hypoglycemia?

Signs and symptoms of hypoglycemia include hunger, fatigue, shaking, sweating, pale skin, headache, and dizziness. If hypoglycemia persists, these signs and symptoms may worsen, resulting in confusion, slurred speech, blurred vision, fainting, seizures, or even coma.

What causes hypoglycemia?

Hypoglycemia most often occurs in people with diabetes as a side effect of taking too much insulin or diabetes medications; it can also be a result of eating less or exercising more than usual.

What causes hypoglycemia in non-diabetics?

Hypoglycemia is less frequent among non-diabetic individuals. When it does happen, it may occur due to prolonged fasting or not eating enough food over a long time. It may also be a side effect of certain medications or alcohol, or it can be a sign of an underlying condition.

Medications 

Hypoglycemia can be a side effect of various medications, including salicylates (e.g. aspirin), beta blockers (e.g. propranolol), some antibiotics (e.g.levofloxacin), some antifungals (e.g. pentamidine), and antimalarials (e.g. quinine). 

Drinking Alcohol 

When blood glucose is low, especially with hunger or fasting, the liver releases stored glucose to maintain healthy glucose levels. However, excessively drinking alcohol may block the liver from releasing this stored glucose and can lead to hypoglycemia. 

Underlying Conditions 

Hypoglycemia may indicate that there’s an underlying condition, such as liver, kidney, or heart disease. Additionally, blood glucose is tightly regulated by the interplay of hormones, such as cortisol, growth hormone, glucagon, and epinephrine. Thus, hormonal imbalances may result in hypoglycemia. Finally, hypoglycemia with no clear cause may indicate the presence of an insulin-producing tumor. Insulinoma is a rare pancreatic tumor that produces extra insulin, while other tumors like mesenchymal tumors may produce an insulin-like growth factor.

What is reactive hypoglycemia?

Reactive hypoglycemia can occur in non-diabetic individuals after eating a carbohydrate-rich meal. This is likely the result of the body producing more insulin than needed. Reactive hypoglycemia can be a sign of having pre-diabetes or being at risk for diabetes

Reactive hypoglycemia can also occur due to dumping syndrome, which can be a consequence of having gastric bypass surgery. Dumping syndrome is characterized by the rapid movement of food from the stomach to the small bowel, which can trigger increased insulin production. However, with this rapid movement of food, most food does not end up getting absorbed into the blood; as a consequence, the excess amount of insulin that is produced can lead to hypoglycemia.

How do you test for hypoglycemia?

If you are diabetic and using insulin or other diabetes medications and you are experiencing symptoms of hypoglycemia, it is important to check your blood sugar with a blood glucose meter. Blood sugar levels below 70 mg/dL confirm hypoglycemia, and levels below 54 mg/dL call for immediate action to raise your blood sugar.

Non-diabetic individuals who experience the symptoms of hypoglycemia may need to consult a physician.

How do you treat hypoglycemia?

To treat hypoglycemia, blood sugar levels must be raised back to healthy values. To do this, people are typically asked to eat or drink 15 grams of fast-acting carbohydrates—for instance, glucose tablets, a fruit juice box, or one tablespoon of sugar or honey are common remedies. As these sugary foods and drinks don’t have any proteins or fats, they are more easily processed in the body. Blood sugar levels should then be rechecked 15 minutes after consuming at least 15 grams of carbohydrates.

If, after 15 minutes have elapsed, blood sugar levels are still below 70 mg/dL, a hypoglycemic person should eat or drink 15 more grams of fast-acting carbohydrates and recheck their blood sugar levels after another 15 minutes. This is generally referred to as the 15-15 rule, and is repeated until their blood sugar levels are above 70 mg/dL. Once recovered and no longer in a hypoglycemic state, people typically benefit from eating a more substantial snack or meal.

Individuals suffering from severe hypoglycemia may need assistance to recover. If someone is unconscious and cannot eat, they may require a glucagon injection. Generally, diabetic individuals will have a glucagon kit for emergencies. However, if there is no kit available, those helping should call 911.

How do you prevent hypoglycemia?

A variety of measures can be taken to prevent hypoglycemia from occurring. Individuals who have diabetes or are struggling with reactive hypoglycemia should try to include more complex carbohydrates in their diet. Examples of complex carbohydrates include whole grains, beans, and vegetables such as broccoli. Unlike simple carbohydrates (such as honey, sugar, and fruits), complex carbohydrates take longer for the body to break down, which helps maintain blood glucose levels constant over a longer period of time. 

If hypoglycemia frequently recurs in a diabetic individual, their physician may suggest changing, stopping, or adjusting their dosage of their insulin or diabetes medications. 

In non-diabetic individuals, treatment of underlying conditions may be necessary to resolve the associated hypoglycemia.

What are the most important facts to know about hypoglycemia?

Hypoglycemia is a term that describes low blood sugar levels below 70 mg/dL. It is most common among diabetic individuals as a side effect of treatment. However, it can also occur in non-diabetic individuals due to certain medications, prolonged fasting, not eating enough food, or an underlying condition. Symptoms include hunger, fatigue, shaking, sweating, headache, dizziness, confusion, slurred speech, blurred vision, fainting, seizures, or even coma. Hypoglycemia can be tested for by checking blood sugar levels, and must be treated immediately by replenishing the glucose with at least 15 grams of carbohydrates, usually through glucose tablets, fruit juice, or sugary candies. Unconscious individuals may require a glucagon injection. Finally, non-diabetic individuals experiencing hypoglycemia should consult a physician in order to assess for potential underlying conditions. 

Related links

Alcohol use disorder
Clinical reasoning: Diabetes mellitus
Diabetes mellitus
Pancreatic cancer

Resources for research and reference

Altuntaş, Y. (2019). Postprandial Reactive Hypoglycemia. SiSli Etfal Hastanesi Tip Bulteni / The Medical Bulletin of Sisli Hospital, 53(3): 215–220. DOI: 10.14744/semb.2019.59455

Anno, T., Kaneto, H., Shigemoto, R., Kawasaki, F., Kawai, Y., Urata, N., Kawamoto, H., Kaku, K., & Okimoto, N. (2018). Hypoinsulinemic hypoglycemia triggered by liver injury in elderly subjects with low body weight: Case reports. Endocrinology, Diabetes & Metabolism Case Reports, 1. DOI: 10.1530/edm-17-0155

Kalra, S., Mukherjee, J., Venkataraman, S., Bantwal, G., Shaikh, S., Saboo, B., Das, A., & Ramachandran, A. (2013). Hypoglycemia: The neglected complication. Indian Journal of Endocrinology and Metabolism, 17(5): 819–34. DOI: 10.4103/2230-8210.117219

Morales, J. & Schneider, D. (2014). Hypoglycemia. The American Journal of Medicine, 127(10 suppl): S17–24. DOI: 10.1016/j.amjmed.2014.07.004

Parekh, T. M., Raji, M., Lin, Y., et al. (2014). Hypoglycemia After Antimicrobial Drug Prescription for Older Patients Using Sulfonylureas. JAMA Internal Medicine, 174(10): 1605–1612. DOI: 10.1001/jamainternmed.2014.3293

Vue, M. H. & Setter, S. M. (2011). Drug-Induced Glucose Alterations Part 1: Drug-Induced Hypoglycemia. Diabetes Spectrum, 24(3): 171-177. DOI: 10.2337/diaspect.24.3.171