Spanish Version
Print-Friendly
Bookmarks
bookmarks-menu

Low blood sugar

Hypoglycemia; Insulin shock; Insulin reaction; Diabetes - hypoglycemia

Low blood sugar is a condition that occurs when the body's blood sugar (glucose) decreases and is too low.

Blood sugar below 70 mg/dL (3.9 mmol/L) is considered low. Blood sugar at or below this level can be harmful.

The medical name of low blood sugar is hypoglycemia.

Causes

Insulin is a hormone made by the pancreas. Insulin is needed to move glucose into cells where it is stored or used for energy. Without enough insulin, glucose builds up in the blood instead of going into the cells. This leads to symptoms of diabetes.

Low blood sugar occurs due to any of the following:

  • Your body's sugar (glucose) is used up too quickly
  • Glucose production by the body is too low or it is released into the bloodstream too slowly
  • Too much insulin is in the bloodstream

Low blood sugar is common in people with diabetes who are taking insulin or certain other medicines to control their diabetes. However, many other diabetes medicines do not cause low blood sugar.

Exercise can also lead to low blood sugar in people taking insulin to treat their diabetes.

Babies born to mothers with diabetes may have severe drops in blood sugar right after birth.

In people who do not have diabetes, low blood sugar may be caused by:

  • Drinking alcohol
  • Insulinoma, which is a rare tumor in the pancreas that produces too much insulin
  • Lack of a hormone, such as cortisol, growth hormone, or thyroid hormone
  • Severe heart, kidney, or liver failure
  • Infection that affects the whole body (sepsis)
  • Some types of weight-loss surgery (usually 5 or more years after the surgery)
  • Medicines not used to treat diabetes (certain antibiotics or heart drugs)

Symptoms

Symptoms you may have when your blood sugar gets too low include:

  • Double vision or blurry vision
  • Fast or pounding heartbeat
  • Feeling cranky or acting aggressive
  • Feeling nervous
  • Headache
  • Hunger
  • Shaking or trembling
  • Sweating
  • Tingling or numbness of the skin
  • Tiredness or weakness
  • Trouble sleeping
  • Unclear thinking

In many people with diabetes, low blood sugar occurs every time with nearly the same symptoms.

Some symptoms, like hunger or sweating, occur when blood sugar is only slightly low. More severe symptoms, such as unclear thinking or seizure, occur when the blood sugar is much lower (less than 40 mg/dL or 2.2 mmol/L).

Even if you do not have symptoms, your blood sugar could still be too low (called hypoglycemic unawareness). You may not even know you have low blood sugar until you faint, have a seizure, or go into a coma. If you have diabetes, ask your health care provider if wearing a continuous glucose monitor and sensor can help you detect when your blood sugar is getting too low to help prevent symptoms.

If you have diabetes, keeping good control of your blood sugar can help prevent low blood sugar. Talk to your provider if you're not sure about the causes and symptoms of low blood sugar.

Exams and Tests

When you have low blood sugar, the reading will be lower than 70 mg/dL (3.9 mmol/L) on your glucose monitor.

Your provider may ask you to wear a small monitor that measures your blood sugar every 5 minutes (continuous glucose monitor). The device is often worn for 3 or 7 days. The data is downloaded to find out if you're having periods of low blood sugar that are going unnoticed.

If you're admitted to the hospital, you'll likely have blood samples taken from your vein to:

  • Measure your blood sugar level
  • Diagnose the cause of your low blood sugar (these tests need to be carefully timed related to low blood sugar to make an accurate diagnosis)

Treatment

The goal of treatment is to correct your low blood sugar level.

If you have diabetes, it is likely your provider told you how to treat yourself for low blood sugar. Treatment may include:

  • Drinking juice
  • Eating food
  • Taking glucose tablets

Or you may have been told to give yourself a shot of glucagon. This is a medicine that raises blood sugar.

If low blood sugar is caused by an insulinoma, surgery to remove the tumor will be recommended.

Possible Complications

Severe low blood sugar is a medical emergency. It can cause seizures and brain damage. Severe low blood sugar that causes you to become unconscious is called hypoglycemic or insulin shock.

Even one episode of severe low blood sugar may make it less likely for you to have symptoms that allow you to recognize another episode of low blood sugar.

When to Contact a Medical Professional

If signs of low blood sugar do not improve after you have eaten a snack that has sugar:

  • Get a ride to the emergency room. DO NOT drive yourself.
  • Call a local emergency number (such as 911)

Get medical help right away for a person with diabetes or low blood sugar who:

  • Becomes less alert
  • Cannot be woken up

References

American Diabetes Association. 6. Glycemic targets: standards of medical care in diabetes - 2018. Diabetes Care. 2018;41(Suppl 1):S55-S64. PMID: 29222377 www.ncbi.nlm.nih.gov/pubmed/29222377.

Davis SN, Lamos EM, Younk LM. Hypoglycemia and hypoglycemic syndromes. In: Jameson JL, De Groot LJ, de Kretser DM, et al, eds. Endocrinology: Adult and Pediatric. 7th ed. Philadelphia, PA: Elsevier Saunders; 2016:chap 47.

BACK TO TOP Text only

  • Food and insulin release - illustration

    Insulin is a hormone secreted by the pancreas in response to increased glucose levels in the blood.

    Food and insulin release

    illustration

  • 15/15 rule - illustration

    To treat low blood sugar the 15/15 rule is usually applied. Eat 15 grams of carbohydrate and wait 15 minutes. The following foods will provide about 15 grams of carbohydrate: 3 glucose tablets; half a cup (4 ounces or 120 milliliters) of fruit juice or regular soda; 6 or 7 hard candies; or 1 tablespoon (15 grams) of sugar. After the carbohydrate is eaten, the person should wait about 15 minutes for the sugar to get into their blood. If the person does not feel better within 15 minutes, more carbohydrate can be consumed. Their blood sugar should be checked to make sure it has come within a safe range.

    15/15 rule

    illustration

  • Food and insulin release - illustration

    Insulin is a hormone secreted by the pancreas in response to increased glucose levels in the blood.

    Food and insulin release

    illustration

  • 15/15 rule - illustration

    To treat low blood sugar the 15/15 rule is usually applied. Eat 15 grams of carbohydrate and wait 15 minutes. The following foods will provide about 15 grams of carbohydrate: 3 glucose tablets; half a cup (4 ounces or 120 milliliters) of fruit juice or regular soda; 6 or 7 hard candies; or 1 tablespoon (15 grams) of sugar. After the carbohydrate is eaten, the person should wait about 15 minutes for the sugar to get into their blood. If the person does not feel better within 15 minutes, more carbohydrate can be consumed. Their blood sugar should be checked to make sure it has come within a safe range.

    15/15 rule

    illustration

A Closer Look

 

Self Care

 

Tests for Low blood sugar

 
 

Review Date: 2/22/2018

Reviewed By: Brent Wisse, MD, Associate Professor of Medicine, Division of Metabolism, Endocrinology & Nutrition, University of Washington School of Medicine, Seattle, WA. Also reviewed by David Zieve, MD, MHA, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.

The information provided herein should not be used during any medical emergency or for the diagnosis or treatment of any medical condition. A licensed medical professional should be consulted for diagnosis and treatment of any and all medical conditions. Links to other sites are provided for information only -- they do not constitute endorsements of those other sites. © 1997- A.D.A.M., a business unit of Ebix, Inc. Any duplication or distribution of the information contained herein is strictly prohibited.
adam.com

 
 
 

 

 

A.D.A.M. content is best viewed in IE9 or above, Firefox and Google Chrome browser.
Content is best viewed in IE9 or above, Firefox and Google Chrome browser.