What Is the Most Common Cause of Low Blood Sugar?

Reviewed on 6/10/2022
A person using a blood sugar finger test
The most common causes of low blood sugar in people with diabetes include taking too much medicine (insulin or certain oral diabetes drugs), not eating enough carbohydrates for the amount of insulin taken, not eating enough food, the amount of fat, protein, and fiber in meals; timing of when insulin is taken, waiting too long between meals, drinking too much alcohol, too much exercise without eating a snack or reducing insulin dosage, hot and humid weather, unexpected changes in schedule, time spent at high altitude, going through puberty, and menstruation.

Low blood sugar (hypoglycemia) is when the level of sugar (glucose) in the blood gets too low, usually below 70 mg/dL.

Low blood sugar most commonly occurs in people who have diabetes. The most common causes of low blood sugar in diabetics include:

  • Taking too much medicine, including insulin or certain oral diabetes drugs
  • Not eating enough carbohydrates for the amount of insulin taken
  • Not eating enough food
  • The amount of fat, protein, and fiber in meals
  • Timing of when insulin is taken
  • Waiting too long between meals
  • Drinking too much alcohol
  • Too much exercise without eating a snack or reducing insulin dosage
  • Hot and humid weather
  • Unexpected changes in schedule
  • Time spent at high altitude
  • Going through puberty
  • Menstruation

Low blood sugar is very uncommon in people who are not diabetic. Causes of low blood sugar in non-diabetics includes:

What Are Symptoms of Hypoglycemia?

Early symptoms of low blood sugar (hypoglycemia) can include:

If low blood sugar is not treated, it can lead to severe symptoms, such as:

  • Lightheadedness
  • Fainting
  • Headache
  • Weakness
  • Vision problems
  • Problems walking
  • Tingling or numbness in the lips, tongue, or cheeks
  • Not thinking clearly
  • Acting strangely 
  • Confusion
  • Seizures

Some people with diabetes may not have symptoms during early stages of low blood sugar in what is called “hypoglycemia unawareness.” Since people with hypoglycemia unawareness do not have symptoms, they do not treat low blood sugar early, and they are more likely to have severe symptoms. Hypoglycemia unawareness often occurs in people who:

  • Use insulin to control blood sugar levels
  • Frequently have low blood sugar
  • Have had type 1 diabetes for more than 5 to 10 years
  • Drink a lot of alcohol
  • Are tired
  • Take medicines for high blood pressure such as beta blockers


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How Is Low Blood Sugar Diagnosed?

Low blood sugar (hypoglycemia) is diagnosed when a person has symptoms of low blood sugar and:

  • Low blood sugar levels are present when symptoms occur 
    • Measured with a blood test from a blood glucose meter (usually less than 60 mg/dL)
  • The person feels better after eating something that raises blood sugar levels to normal

Tests to help determine the cause of low blood sugar may include: 

What Is the Treatment for Low Blood Sugar?

Treatment for low blood sugar (hypoglycemia) includes:

  • Consuming quick sources of sugar 
    • Glucose tablets or gel
    • Fruit juice
    • Regular soda
    • Sugary candy such as jelly beans, gumdrops, or hard candies
    • Honey
    • Corn syrup
    • Diabetics should carry a quick source of sugar at all times
  • Glucagon, a hormone, used to quickly raise blood sugar levels and stop severe symptoms

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Reviewed on 6/10/2022
Image Source: iStock Images