Low blood sugar, also known as hypoglycemia, happens when your blood sugar (glucose) drops below a healthy range. If your blood sugar drops too low, it can be a dangerous condition that needs immediate treatment.
Your blood sugar is considered low when it drops below 70 mg/dL.
Hypoglycemia is most common in people with diabetes. Taking too much medication (specifically sulfonylureas or insulin), skipping meals, not eating enough, or exercising more than usual can lead to low blood sugar if you have diabetes.
In rare cases, hypoglycemia may be a result of other conditions or some types of drugs.
This article will take a closer look at hypoglycemia, as well as the symptoms and treatment and how to prevent your blood sugar from dropping too low.
Blood sugar is also known as glucose. Glucose comes from food and serves as an important energy source for your body. Carbohydrates — found in foods such as rice, potatoes, bread, tortillas, cereal, fruit, vegetables, and milk — are your body’s main source of glucose.
After you eat, glucose is absorbed into your bloodstream, where it travels to your body’s cells. A hormone called insulin, which is made in your pancreas, helps your cells absorb the glucose (sugar) in your blood. Your cells then use the glucose for energy.
If you eat more glucose than you need, your body will store the extra glucose in your liver and muscles or change it into fat so it can be used for energy when it’s needed later.
If your cells don’t get glucose, your body can’t perform its normal functions. In the short term, people who aren’t on medications that increase insulin have enough glucose to maintain blood sugar levels, and the liver can make glucose if needed.
However, if you take insulin medication, a short-term reduction in blood glucose can cause problems. In this situation, immediate treatment for low blood sugar levels is very important to prevent more serious symptoms from developing.
Symptoms of low blood sugar can occur suddenly. They include:
- pale skin
- unexplained fatigue
- rapid heartbeat
- mood changes
- difficulty sleeping
- skin tingling
- blurry vision
- trouble thinking clearly or concentrating
- loss of consciousness, seizure, or coma
People with hypoglycemic unawareness do not know their blood sugar is dropping. If you have this condition, your blood sugar can drop without you noticing it.
Without immediate treatment, you may faint, experience a seizure, or even go into a coma.
What to do if you have low blood sugar symptoms
If you have diabetes and are experiencing mild to moderate hypoglycemia symptoms, you need to immediately eat or drink 15 grams of easily digestible carbohydrates.
Examples of easily digestible carbohydrates
- 1/2 cup of juice or regular soda
- 1 tablespoon of honey
- 4 or 5 saltine crackers
- 3 or 4 pieces of hard candy or glucose tablets
- 1 tablespoon of sugar
Very low blood sugar is a medical emergency. If you or someone else with diabetes is experiencing severe symptoms, such as unconsciousness, it’s important to administer a medication called glucagon and contact emergency services immediately.
If you’re at risk for low blood sugar, it’s important to talk with your doctor about getting a prescription for glucagon.
You should never give an unconscious person anything by mouth, as it could cause them to choke. If you have diabetes, make sure your family and friends know not to do this if you lose consciousness.
Low blood sugar can occur for a number of reasons. It’s usually a side effect of diabetes treatment.
Possible causes with diabetes
Diabetes affects your body’s ability to use insulin. Think of insulin as the key that unlocks your cells, letting in glucose for energy.
If you have diabetes, a variety of treatments can help the cells in your body use the glucose in your blood. Among these are insulin injections and oral medications that increase insulin production.
If you take too much of these types of medications, your blood sugar may drop too low. You may also sometimes experience low blood sugar if you plan to eat a big meal but then do not eat enough.
Skipping meals, eating less than usual, or eating later than usual but taking your medication at your usual time can also lead to low blood sugar levels.
Unplanned excess physical activity without eating enough can also cause a drop in blood sugar levels.
Drinking alcohol when you’re on these medications can also lead to low blood sugar, especially if it replaces food. When your body is trying to get rid of alcohol, it becomes worse at managing blood sugar levels.
Possible causes without diabetes
Even if you don’t have diabetes, you may experience low blood sugar. However, hypoglycemia is much less common in people without diabetes.
Some possible causes of low blood sugar in people who don’t have diabetes are:
If you suspect you have low blood sugar, it’s important to check your blood sugar right away. If you don’t have a blood glucose meter and you’re on diabetes medications that increase insulin, talk with your doctor about getting a meter.
If you experience low blood sugar often — say, a few times a week — see your doctor right away to find out why. Your doctor will begin your visit by requesting your medical history, asking questions about your eating habits, and learning more about the symptoms you’re experiencing.
If you don’t have diabetes but suspect you have hypoglycemia, talk with your doctor about your symptoms. Your doctor will use three criteria, sometimes referred to as “Whipple’s triad,” to diagnose low blood sugar:
- Signs and symptoms of low blood sugar. Your doctor may require you to fast, or abstain from drinking and eating for an extended period of time, so they can observe your low blood sugar signs and symptoms.
- Documentation of low blood sugar when your signs and symptoms occur. Your doctor will order a blood test to analyze your blood sugar levels in a laboratory.
- Disappearance of the signs and symptoms of low blood sugar. Your doctor will want to know whether the signs and symptoms go away when your blood sugar levels are raised.
Your doctor may send you home with a blood glucose meter — a small handheld blood testing device — to track your blood sugar over time at home. They will give you instructions to test your blood sugar during certain times of the day, such as after waking up and after eating meals.
How to test your blood sugar at home
To perform a blood sugar test, you will need to prick your finger with a lancet (provided in your blood glucose test kit). You’ll put a small sample of blood from this onto a strip inserted into the blood glucose meter.
Before you test your blood sugar at home, it’s important to find out from your doctor what a healthy blood sugar range is for you. Your doctor will determine this range based on factors such as:
- the type of diabetes you have
- how long you’ve had diabetes
- your age
- whether you have any other chronic health conditions
If you don’t have a blood sugar testing machine on hand and are experiencing signs or symptoms of low blood sugar with diabetes, your symptoms may be enough to diagnose low blood sugar.
When your blood sugar levels are too low, eating carbohydrates is key. If you have diabetes, try to keep high carbohydrate snacks on hand.
The American Diabetes Association recommends that your snack have at least 15 grams of carbohydrates. Some good snacks to keep on hand are:
- hard candies
- non-diet soda or juice
- honey or table sugar
- jelly beans or gumdrops
- fresh or dried fruit
You also can take glucose tablets to rapidly raise your blood sugar if it’s low. These are available without a prescription. It’s important to check how many grams are in each tablet before taking them. Aim to get 15 to 20 grams of carbohydrates.
Wait 15 minutes after eating or taking a glucose tablet and test your blood sugar again. If your blood sugar is not going up, eat another 15 grams of carbohydrates or take another dose of glucose tablets. Repeat this until your blood sugar level starts to rise.
Be sure not to overeat. This could lead to blood sugar levels that are too high.
If your blood sugar remains unresponsive, contact your doctor or emergency services right away. When in doubt, treat.
Symptoms of low blood sugar usually get worse if they’re left untreated. Make an appointment to see your doctor if you have diabetes and experience low blood sugar levels often, or if you have symptoms, even if you don’t have diabetes.
Mildly low blood sugar levels are somewhat common for people with diabetes. However, severely low blood sugar levels can be life threatening. They may lead to seizures and nervous system damage if left untreated long enough. Immediate treatment is critical.
It’s important to recognize your symptoms and treat them quickly. For people at risk for low blood sugar, having a glucagon kit — a medication that raises blood sugar levels — is important. Talk with your doctor for more information.
You may also want to talk with friends, family members, exercise partners, and co-workers about how to care for you if your blood sugar drops too low.
It’s important for them to recognize low blood sugar symptoms and to know how to use the glucagon kit, as well as understand the importance of calling 911 if you lose consciousness.
Wearing a medical identification bracelet is a good idea. It can help emergency responders care for you properly if you need urgent medical attention.
Treat low blood sugar as soon as possible. Avoid driving if you are experiencing low blood sugar, as it can increase your risk for having an accident.
There are several ways you can prevent low blood sugar. We’ll look at each of these prevention methods in more detail below.
Check your blood sugar often
Regularly checking your blood sugar level can help you keep it in your target range. If you’ve had low blood sugar episodes in the past, you may want to check your blood sugar levels before driving or operating machinery.
Talk with your doctor about when and how often you should check your blood sugar.
Consider having a snack before you leave your home if you know it will be more than 5 hours until your next full meal or if your blood sugar levels are less than 100 mg/dL.
It’s a good idea to keep carbohydrate-rich snacks on hand at all times in case your blood sugar dips while you’re out and about. As mentioned above, some good choices are hard candies, fresh or dried fruit, fruit juice, jelly beans, and gumdrops.
Fuel during exercise
Exercise uses up energy, so it can quickly cause your blood sugar to drop if you haven’t eaten enough beforehand. Check your blood sugar 1 to 2 hours before exercising to make sure it’s within your target range.
If it’s too low, eat a small meal or carbohydrate-rich snack.
If you plan to exercise for an hour or longer, consume additional carbohydrates during your workout. Exercise gels, sports drinks, granola bars, and even candy bars can provide your body with a quick burst of glucose during exercise.
Work with your healthcare team to come up with the right program for you.
Moderate to intense exercise can cause blood glucose to drop for up to 24 hours afterward. It’s important to check your blood glucose immediately after exercise and every 2 to 4 hours afterward until you go to sleep. Avoid intense exercise immediately before bed.
Listen to your doctor
If you follow a meal plan or take medications that increase insulin to manage low blood sugar, it’s important to stick to the plan your doctor prescribed to help prevent drops in your blood sugar level.
Not eating the right foods or taking the right medications at the correct times can cause your blood sugar to drop. Check in often with your doctor so they can adjust your treatment plan if and when necessary.
I just started a weight loss program, and I keep having a big drop in my blood sugar levels after breakfast. Any advice?
It sounds like you may be experiencing something called reactive hypoglycemia, or low blood sugar after eating a meal, which is most likely due to a change in diet.
To manage this problem, I recommend consistent and frequent meals and snacks every 3 to 4 hours that are a mix of high fiber carbohydrates, fat, and protein.
Eating high fiber carbohydrates is important because they provide the sugar the body needs, but they are also what causes the body to release insulin.
Make sure to add some protein or fat to all of your meals and snacks. Protein and fat can help slow the digestion of carbohydrates, which helps manage the release of insulin and allows for the slow and steady digestion of carbs.
Be sure to discuss any changes to your diet with your primary care physician.
— Peggy Pletcher, MS, RD, LD, CDCES
Answers represent the opinions of our medical experts. All content is strictly informational and should not be considered medical advice.
Hypoglycemia, also known as low blood sugar, can happen when your blood sugar drops below a healthy range. Your blood sugar is considered low when it drops below 70 mg/dL.
Hypoglycemia is most common in people with diabetes. Although this is a lot less common, hypoglycemia can also happen to people who don’t have diabetes. This is typically caused by medications or a medical condition.
Some of the most common symptoms of hypoglycemia are shakiness, dizziness, hunger, irritability, and fatigue, as well as pale skin, a rapid heartbeat, headache, sweating, and lack of concentration.
If you’re experiencing mild or moderate symptoms, it’s important to eat or drink 15 grams of easily digestible carbohydrates right away. If your blood sugar drops too low, it can be a dangerous condition that needs immediate treatment.