Why Blood Sugar Can Get Too Low—And What to Do About It

Symptoms of low blood sugar can include sweating, shakiness, and confusion.

Low blood sugar is something that people, especially those with diabetes, may experience. The condition of blood sugar being too low is known as hypoglycemia. Initial symptoms can include shakiness, irritability, and confusion. 

Hypoglycemia can decrease quality of life. It can also be harmful if its symptoms leads to a fall or other injury. In severe instances, low blood sugar can become a medical emergency.

Fortunately, low blood sugar is treatable. People with diabetes and those caring for them should learn to recognize hypoglycemia as soon as symptoms begin so that the condition can be treated properly and quickly.

woman with diabetes checking her blood sugar
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What Causes Low Blood Sugar?

It’s normal for blood sugar levels to go up and down throughout the day. Within two hours of starting a meal, the typical blood sugar target for someone with diabetes is less than 180 milligrams per deciliter (mg/dL). Before a meal, the level should be 80 to 130mg/dL. These targets may be different for you based on factors like age and other health conditions you may have.

Sometimes, blood sugar levels can be too low under your target. This is known as hypoglycemia. The American Diabetes Association classifies hypoglycemia into three different categories:

  • Level 1: Your blood sugar is less than 70mg/dL but at least 54mg/dL. Negative effects may be starting.
  • Level 2: Your blood sugar is less than 54mg/dL. Immediate action is needed to reverse the low levels and their effects on your function.
  • Level 3: Your mental and/or physical functioning has changed so severely that another person needs to aid in your recovery.

People with diabetes who are treated with insulin or certain diabetes medications, such as oral medications that increase insulin secretion, are at highest risk for low blood sugar. In fact, a large global study of people with diabetes who take insulin found that 83% of people with type 1 diabetes and 46.5% of those with type 2 diabetes reported a low blood sugar event at least once over a four-week period. 

People with diabetes experience low blood sugar when there isn’t enough glucose in the bloodstream to supply the body with energy. This can happen for a variety of reasons, including:

  • Exercising, depending on the intensity and duration
  • Taking too much of your diabetes medication (such as insulin)
  • Not eating enough carbohydrates 
  • Missing or delaying meals  
  • Drinking alcohol

It is rarer for people without diabetes to have hypoglycemia, but it is possible. People who don't have diabetes may experience low blood sugar if they have: 

  • Reactive hypoglycemia, a condition that causes low blood sugar two to five hours after eating
  • Certain genetic disorders, such as congenital hyperinsulinism, when too much insulin is produced
  • Kidney and liver disease
  • Hormonal deficiencies

How to Tell If Your Blood Sugar Is Low

Symptoms of hypoglycemia are different for everyone and can occur at different blood sugar levels. 

Early-stage symptoms of hypoglycemia include:

  • Increased heartbeat
  • Sweating
  • Anxiety
  • Feeling shaky or dizzy
  • Unusual hunger
  • Confusion or irritability

Early symptoms may be subtle or hard to detect. Sometimes you may not experience any symptoms—this is known as hypoglycemia unawareness. People who have had diabetes for five to 10 years, who have low blood sugar often, or who take certain medications are more likely to have hypoglycemia unawareness. Hypoglycemia unawareness is also common for people who have nocturnal hypoglycemia—low blood sugar in the middle of the night that often goes undetected.

Young children and the elderly are also vulnerable to low blood sugar because of their reduced ability to recognize symptoms and communicate them.

Not knowing you have low blood sugar can delay treatment, causing your blood sugar levels to drop to more dangerous levels.

The symptoms of later stages of hypoglycemia are more serious and obvious:

  • Loss of coordination
  • Lethargy
  • Weakness
  • Personality changes
  • Loss of consciousness
  • Seizure

If you have diabetes and are using insulin or taking other medications that can cause your blood sugar to drop, you should have access to a blood glucose monitor. People with diabetes also use various forms of continuous glucose monitors (CGMs) to track their blood sugar. If you suspect you have low blood sugar based on symptoms or your CGM is alerting you that your levels are low, you can test with the blood glucose monitor to confirm.

Depending on which CGM device you are using, you may not need to test before making treatment decisions. CGMs such as real-time CGMs and intermittently scanned CGMs do not have this requirement. However, if your CGM is telling you your blood sugar is low and you don't feel it, you may want to check to confirm. Discuss with a healthcare provider how to handle low blood sugars when using a CGM.

It may not always be possible to check levels when experiencing symptoms of low blood sugar, but knowing the symptoms and how to treat them can help prevent a medical emergency for yourself or the person for whom you care.

How to Raise Low Blood Sugar

If you are having symptoms of low blood sugar and have diabetes, you should test your blood glucose levels. If low levels are confirmed, you should treat it right away to prevent symptoms from becoming worse. 

Blood sugar can be treated, or brought back to normal levels, by ingesting rapid-acting carbohydrates. The recommended treatment approach is the 15-15 rule.

First, ingest 15g of carbohydrates that contain glucose. Options include:

  • Three to four glucose tablets
  • 4oz of any fruit juice or regular (non-diet) soda
  • Five to six pieces of hard candy
  • 1tbsp of honey, sugar, or jelly

Avoid choices that are high in fat, such as chocolate or candies with nuts. These types of carbohydrates may not be metabolized as quickly and can take longer to bring blood sugar up to safe levels.

Re-test your blood sugar levels 15 minutes after you take in the carbohydrates. If your blood sugar has not gone up, the treatment should be repeated. Not everyone may need 15g of carbohydrates to stabilize their levels. For example, children may need fewer carbohydrates. Talk with a healthcare provider to figure out how much you need ingest to raise your levels.

Once blood sugar is trending up, eat a meal or snack that contains a complex carbohydrate, protein, and fat to make sure levels don’t fall again. For example, eat a sandwich on whole grain bread made with nut butter, cheese, or a protein source like chicken. If you are on-the-go, you may choose to grab a yogurt, nuts, and fruit or a meal-replacement bar.

If blood sugar stays low for too long it can starve the brain of glucose. This can lead to complications like seizures, coma, and very rarely death. Because of this, it is recommended that people with diabetes who are at increased risk of developing level 2 or 3 hypoglycemia be prescribed glucagon. Glucagon is a hormone used to raise severely low blood sugar when you are unable to follow the 15-15 rule. It is administered when a person can't ingest carbohydrates because they are unresponsive.

Glucagon is a life-saving prescription. Caretakers of children and adults people with diabetes, school personnel, and camp counselors should know how to use glucagon in case of an emergency.

If you don't have diabetes and experience an episode of low blood sugar, you should eat a snack or meal that contains carbohydrates, fat, and protein to prevent blood sugar from dropping lower.

If you frequently experience symptoms of low blood sugar—with or without diabetes—you should consider going to a healthcare provider to determine the reason and whether a change in any treatment plan is needed.

Preventing Low Blood Sugar

Understanding the causes of low blood sugar and preventing those causes can help prevent low blood sugar. For people with diabetes, another key to prevention is frequently monitoring your blood sugar levels. Even people with diabetes who closely track their levels can experience low blood sugar—sometimes as much as twice a week. So on top of monitoring your blood sugar levels, along with speaking with your doctor about possible medication side effects, prevention also includes keeping a fast-acting carbohydrate on hand.

If you experience low blood sugar while sleeping, you can prevent it by:

  • Not skipping meals during the day
  • Eating when you drink alcohol 
  • Having a snack before bed

When it comes to bedtime snacks, the exact amount of carbohydrate needed will depend on various factors, including blood sugar pre-bedtime, type of insulin being used, and activity level prior to bed. Snacks should contain a fiber-rich carbohydrate, protein, and fat. Options include:

  • Small apple or half a banana with nut butter (peanut, almond, cashew, mixed nut)
  • Berries with Greek yogurt
  • English muffin with cottage cheese
  • 1oz of cheese and handful of whole grain crackers
  • Waffle with nut butter and fruit
  • Whole grain cereal with low-fat milk

A Quick Review

Low blood sugar, or hypoglycemia, is a common condition people with diabetes experience. It is more common among people with type 1 diabetes, but people with type 2 diabetes—and even those without diabetes—can also experience it. 

Understanding the causes of low blood sugar can reduce your risk and prevent it. All people with diabetes—as well as those who care for people with diabetes—should receive education on signs, symptoms, and treatment of low blood sugar. Equip yourself and your loved ones with fast-acting carbohydrates, glucagon, and glucose monitors for proper treatment and prevention of emergencies.

If you have diabetes and are experiencing frequent episodes of low blood sugar, make an appointment with a healthcare provider so that they assist you in detecting why you are having lows and make necessary changes to your regimen. If you do not have diabetes and suspect that you are having low blood sugars, a medical examination can help you determine the cause and proper treatment.

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17 Sources
Health.com uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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