Low Blood Sugar and Insulin Use

Published: November 02, 2021
T Cindy Yang
By Tianrui "Cindy" Yang, Pharm.D., BCPS

Low blood sugar or hypoglycemia can occur during the management of diabetes. Severe hypoglycemia can cause seizures or unconsciousness and requires emergency care. It is important to understand the symptoms of hypoglycemia, how to check your blood sugar, and how to treat it.

What are the causes of hypoglycemia when managing diabetes with insulin?

  • Taking too much insulin
  • Not eating enough carbs for how much insulin you take
  • Timing of when you take your insulin
  • The amount and timing of physical activity
  • Drinking alcohol
  • Unplanned changes in your schedule

What are the symptoms of hypoglycemia?

Common signs and symptoms of hypoglycemia include a feeling of shakiness, nervousness or anxiousness, sweating, chills, irritability or impatience, confusion, fast heartbeat, feeling lightheaded or dizzy, hunger, headaches, nausea, blurred/impaired vision, feeling weak or having no energy, and tingling or numbness in your lips, tongue, or cheeks.

It is very important for you and your family members to learn these signs and symptoms so that hypoglycemia can be treated in a timely manner. If you have any of the above symptoms, you should check your blood sugar to see if it is low.

Hypoglycemia can be one of the most serious effects of insulin. Without treatment, severe hypoglycemia can lead to serious outcomes such as seizure, loss of consciousness, or death.

How should I check my blood sugar at home?

Checking blood sugar at home is very important. The American Diabetes Association generally recommends keeping blood sugar between 80 and 130 milligrams per deciliter (mg/dL) before meals and less than 180 mg/dL (10.0 mmol/L) for the two hours after meals. However, your doctor may set a different target blood sugar for you based on your health conditions.

To check your blood sugar, perform the following steps using a glucose meter:

  • Wash and dry your hands well
  • Insert a test strip into your meter
  • Prick the side of your fingertip with the lancet
  • Touch and hold the edge of the test strip to the drop of blood
  • The meter will display your blood sugar level on a screen after a few seconds
  • Discard the lancets in a designated sharps box 

All glucose meters are a little different, so it is important to always read your user manual for specific instructions.

How do I treat hypoglycemia?

A rule called the 15-15 rule was created to prevent overeating in response to hypoglycemia, which can cause very high blood sugar levels. The 15-15 rule can make the treatment of hypoglycemia easier to remember. When your blood sugar is below 70 mg/dL or if you are experiencing signs and symptoms of low blood sugar, you should consume 15 grams of carbohydrate, wait about 15 minutes, then recheck your blood sugar level. If your blood sugar is still low, consume another 15 grams of carbohydrate and recheck 15 minutes later.

Some examples of food that contain 15 grams of carbohydrate are 3 to 4 glucose tablets, 1 dose of glucose gel, 1/2 cup of orange juice or regular soda (not sugar-free), 1 tablespoon of honey or syrup, 1 tablespoon of sugar, or 5 small sugar cubes. This stepwise method allows your blood sugar to recover to normal levels.

How should serious hypoglycemia be treated?

If hypoglycemia isn’t treated or does not respond to treatment, you may experience serious effects that require help from others such as family members, friends, or co-workers.  If you often have hypoglycemia episodes or are at risk for severe effects, your doctor may prescribe glucagon to treat your symptoms. Glucagon comes as an injection and nasal spray. Your caregivers should know how and when to give glucagon and then call for emergency medical help.


It is important to understand how to best manage your blood sugar if you have diabetes. Insulin is an effective but high-risk medication that can be associated with serious effects such as hypoglycemia.

For more information about diabetes and hypoglycemia, visit:

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