How Hypoglycemia Is Diagnosed

By by Cynthia Perkins, M.Ed.
Updated April 29, 2019
Medically reviewed by Richard N. Fogoros, MD

In This Article

Diagnosing hypoglycemia when you have diabetes is simple: if your blood sugar is 70 milligrams per deciliter (mg/dL) or below as determined by your blood glucose meter, you need to treat it immediately with fast-acting carbohydrates. The American Diabetes Association defines severe hypoglycemia as blood sugar less than 54 mg/dL.

If you don't have diabetes but you have symptoms of hypoglycemia, your doctor will need to figure out the cause, starting with a blood test. Similar to when you have a fever, having low blood sugar is not a disease, it's a condition that indicates that something else is going on in your body.

Self-Checks/At-Home Testing

If you're a person with diabetes, especially when you're newly diagnosed and beginning treatment, you will likely encounter episodes of hypoglycemia on occasion.

Along with the common symptoms of hunger, shakiness, sweating, anxiety, and an irregular heartbeat, you'll be able to tell for sure when you check your blood sugar level using a blood glucose meter.

If your blood sugar reading is 70 mg/dL or below, you will need to treat it right away with fast-acting carbohydrates such as three to four glucose tablets, half a banana, or a granola bar.

Labs and Tests

If you do not have diabetes, schedule a visit with your doctor if you keep having symptoms of hypoglycemia. Your doctor will do a physical exam, medical history, and ask you questions about your symptoms.

Blood Tests

Your doctor will need to see if your blood glucose level is low when you're having symptoms. If you have symptoms of hypoglycemia after you eat, your doctor may have you come back after a meal to check your blood glucose.

You may not have symptoms of hypoglycemia while you're in your doctor's office. You may be asked to fast until you develop symptoms, at which time you'll return to your doctor and have your glucose levels checked.

In some cases, you may need to do an extended fast in the hospital, where you can be monitored and your glucose level can be checked periodically. Your doctor may have your blood drawn and sent to the lab to analyze your insulin levels and/or other substances in your blood.

If you do have hypoglycemia, the cause can be as simple as a medication you're taking that can lead to low blood sugar, like the antibiotic Bactrim (sulfamethoxazole and trimethoprim), beta blockers, monoamine oxidase inhibitors (MAOIs), or Haldol (haloperidol), or the result of an alcohol binge.

If it's not due to medications or alcohol, your doctor may do additional testing to find out what the underlying cause is, such as a hormonal deficiency or an illness like kidney disease or hepatitis.

Differential Diagnoses

If you don't have diabetes and you have symptoms of hypoglycemia yet your blood sugar levels are normal, there's something else going on. In fact, there's a long list of conditions that your symptoms could be attributed to.

The most common non-diabetes causes include:

  • Cardiac disease
  • Medication side effects
  • A mental health disorder like generalized anxiety disorder
  • A metabolic disorder like hyperthyroidism

Your doctor may do additional testing to look for the cause of your symptoms depending on what they are and your family and medical history.

If you have diabetes and your blood glucose levels are too low, but you have few or no symptoms, it is probably due to hypoglycemia unawareness.

When you have repeated episodes of hypoglycemia, you can stop showing symptoms. In this case, the hypoglycemia commonly happens at night when you're unaware that your glucose levels have dropped.

A continuous glucose monitor can be helpful to detect hypoglycemia, especially at night, because it alerts you when your levels get too high or too low. Your doctor will also work with you to get your levels under control so this stops happening. Even two to three weeks of avoiding hypoglycemia can restore your body's awareness.

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