Hypoglycemia

Causes and How to Prevent Hypoglycemia (Low Blood Glucose)

What causes low blood glucose?

Young man in workout gear after exercise

Hypoglycemia (or low blood glucose) is common for people with type 1 diabetes. It also can occur in people with type 2 diabetes taking insulin or certain diabetes medications. 

The average person with type 1 diabetes has low blood glucose levels up to twice a week, and that’s only counting episodes with symptoms. If you add in lows without symptoms and the ones that happen overnight, the number would likely be higher.

Common Causes of Low Blood Glucose 

Insulin and similar medications 

Too much insulin or certain diabetes medications is a common cause of low blood glucose. Miscalculating for how many carbs you've eating can lead to giving too much insulin, resulting in a low. But there are a few other ways insulin can cause hypoglycemia. 

  • Accidentally injecting the wrong insulin type. This can happen if you use both short and long acting insulin. If this happens to you, try using something on your insulin vials to tell them apart, like this Insulin Vial Protective Sleeve.
  • Too much insulin. This can happen by miscalculating carbs you've eaten, forgetting you already gave yourself insulin, or other similar circumstances.
  • Injecting directly into the muscle (instead of just under the skin), can cause low blood glucose. Inject into fatty areas like your thighs, stomach, buttocks, or the back of your arm.

Talk to your health care provider to find out if other medications you are taking could affect your blood glucose.  

What You Eat or Drink 

What you eat or drink can has a big impact on your glucose levels. Sometimes, it can lead to a low when the following occurs. 

  • Not eating enough food. If you start eating smaller portions (or even when you start trying to make healthier food choices), eat less carbs then you planned to, or skip a meal or snack, it can lead to a low.  
  • When meals are delayed.
  • Alcohol, especially on an empty stomach. Alcohol use can cause dangerously low blood glucose, leading to a severe hypoglycemia incident. Low blood glucose can also happen many hours after alcohol use. It is very important to monitor your blood glucose closely during and after drinking alcohol. 

Physical Activity 

Physical activity and exercise can lower your blood glucose. Also, more intense physical activity or exercise than usual can make your body more sensitive to insulin and lower your blood glucose levels after you're done.  

This can affect your blood glucose levels for several hours after you've been active, including overnight while you're sleeping. You may need to have a snack before or after exercise. Discuss with your diabetes care team the best ways for you to prevent lows related to exercise and physical activity. 

Why am I having lows? 

If your blood glucose levels are going low and you’re not sure why, bring a log of your glucose levels, with notes about insulin and other medications, physical activity/exercise, and meals and snacks to your diabetes care team. Together, you can review the information to figure out what is causing the lows.  

The more information you have with you to discuss with your health care provider, the more likely it is that you'll be able to figure out what's causing the lows. Your provider may adjust the timing of insulin or other medications, exercise, or meals and snacks to help you prevent low blood glucose. 

Free Resource to Download!

Using a blood glucose log is a convenient way to track when you have low blood glucose. You can add notes on days that you have low blood glucose. Be sure to include your symptoms you had, how you treated it, and your blood glucose level after it was treated. 

Download a free glucose log 

Purchase a blood glucose log book

Blood Glucose Logs

Can low blood glucose be prevented?

Your best bet is to keep your blood glucose in your target range. Keep track of your personal symptoms you feel when go low. If you start to recognize those feelings, you can act faster to treat your low glucose before it drops lower.  

Monitoring blood glucose, with either a blood glucose meter or a continuous glucose monitor (CGM) allows you to be aware of your blood glucose levels and take steps to prevent low blood glucose. Studies consistently show that the more a person checks blood glucose, the lower their risk of low blood glucose.  

 If you can, check with your diabetes care team when and how often your need to check! 

Times you can check include:  

  • Before and after meals.
  • Before and after physical activity including exercise (or during, if it’s a long or intense session).
  • Before bed.
  • In the middle of the night if your blood glucose may go low, such as after a day with intense exercise.
  • After physical activity including exercise 

Check more frequently if things around you change such as a new insulin routine, a different work schedule, an increase in physical activity, or travel across time zones.