Every cell in your body needs energy to function. The main source of energy might come as a surprise: It’s sugar, also known as glucose. Blood sugar is essential to proper brain, heart, and digestive function. It even helps keep your skin and vision healthy.
When your blood sugar levels fall below the normal range, it’s called hypoglycemia. There are many identifiable symptoms of low blood sugar, but the only way to know if you have low blood sugar is by taking a blood glucose test.
Learn more about the symptoms of low blood sugar, as well as the long-term effects on the body.
The most common reasons for low blood sugar are some medications used to treat diabetes, such as insulin.
In type 1 diabetes, the pancreas can no longer produce insulin. In type 2 diabetes, the pancreas doesn’t make enough insulin, or your body can’t use it properly. Too much insulin or oral diabetic medication can lower the blood sugar level, leading to hypoglycemia.
However, contrary to popular belief, low blood sugar isn’t exclusive to diabetes, though it is rare. It can also happen if your body makes more insulin than it should.
Another possible cause of low blood sugar is drinking too much alcohol, especially over long periods of time. This can interfere with the liver’s ability to create a buildup of glucose and then release it into your bloodstream when you need it.
Other causes include:
- kidney disorders
- hepatitis
- liver disease
- anorexia nervosa
- pancreatic tumor
- adrenal gland disorders
- sepsis (usually from very severe infections)
When your blood sugar levels are too low, your cells become starved for energy. At first, you might notice minor symptoms, such as hunger and headaches. However, if you don’t get your blood sugar levels up in time, you may be at risk for serious complications.
To keep blood sugar levels from rising too much — called hyperglycemia — you need the right amount of insulin. With insufficient insulin, your blood sugar levels rise. On the other hand, too much insulin may cause your blood sugar to drop quickly.
Read on to learn how low blood sugar affects your body systems.
After you eat, your digestive system breaks down carbohydrates and turns them into glucose. Essentially, glucose is your body’s fuel source.
As your sugar levels rise, your pancreas releases a hormone called insulin, which helps glucose get taken up and used by cells throughout your body. If you have insulin-dependent diabetes, you must take the right about of insulin to get the job done.
Any excess glucose goes to your liver for storage.
When you go a few hours without eating, blood sugar levels go down. If you have a healthy pancreas, it releases a hormone called glucagon to make up for the absence of food. This hormone tells your liver to process the stored sugars and release them into your bloodstream.
If everything works as it should, your blood sugar levels should remain in the normal range until your next meal.
Insufficient blood sugar levels can cause a rapid heartbeat and heart palpitations. However, even if you have diabetes, you may not always have obvious symptoms of low blood sugar. This is a potentially dangerous condition called hypoglycemia unawareness. It happens when you experience low blood sugar so often that it changes your body’s response to it.
Normally, low blood sugar causes your body to release stress hormones, such as epinephrine. Epinephrine is responsible for those early warning signs, like hunger and shakiness.
When low blood sugar happens too frequently, your body may stop releasing stress hormones, called hypoglycemia-associated autonomic failure, or HAAF. That’s why it’s so important to check your blood sugar levels often.
Oftentimes, low blood sugar can signal immense hunger. However, sometimes low blood sugar can make you lose interest in a meal, even if you’re hungry.
Low blood sugar levels can also cause a variety of problems within your central nervous system. Early symptoms include weakness, lightheadedness, and dizziness. Headaches can occur from a lack of glucose, especially if you have diabetes.
You may also feel signs of stress, such as nervousness, anxiety, and irritability. When blood sugar levels drop during the night, you may have nightmares, cry out during sleep, or other sleep disturbances.
Lack of coordination, chills, clammy skin, and sweating can happen with low blood sugar. Tingling or numbness of the mouth are other effects that may develop. Additionally, you may experience blurred vision, headache, and confusion. Everyday tasks and coordination prove to be difficult too.
Untreated, severe low blood sugar can be very dangerous. It can result in seizures, loss of consciousness, or death.
Overview
Hypoglycemia is a condition in which your blood sugar (glucose) level is lower than the standard range. Glucose is your body's main energy source.
Hypoglycemia is often related to diabetes treatment. But other drugs and a variety of conditions — many rare — can cause low blood sugar in people who don't have diabetes.
Hypoglycemia needs immediate treatment. For many people, a fasting blood sugar of 70 milligrams per deciliter (mg/dL), or 3.9 millimoles per liter (mmol/L), or below should serve as an alert for hypoglycemia. But your numbers might be different. Ask your health care provider.
Treatment involves quickly getting your blood sugar back to within the standard range either with a high-sugar food or drink or with medication. Long-term treatment requires identifying and treating the cause of hypoglycemia.
Symptoms
If blood sugar levels become too low, hypoglycemia signs and symptoms can include:
- Looking pale
- Shakiness
- Sweating
- Headache
- Hunger or nausea
- An irregular or fast heartbeat
- Fatigue
- Irritability or anxiety
- Difficulty concentrating
- Dizziness or lightheadedness
- Tingling or numbness of the lips, tongue or cheek
As hypoglycemia worsens, signs and symptoms can include:
- Confusion, unusual behavior or both, such as the inability to complete routine tasks
- Loss of coordination
- Slurred speech
- Blurry vision or tunnel vision
- Nightmares, if asleep
Severe hypoglycemia may cause:
- Unresponsiveness (loss of consciousness)
- Seizures
When to see a doctor
Seek medical help immediately if:
- You have what might be hypoglycemia symptoms and you don't have diabetes
- You have diabetes and hypoglycemia isn't responding to treatment, such as drinking juice or regular (not diet) soft drinks, eating candy, or taking glucose tablets
Seek emergency help for someone with diabetes or a history of hypoglycemia who has symptoms of severe hypoglycemia or loses consciousness.
Sign up for free, and stay up to date on research advancements, health
tips and current health topics, like COVID-19, plus expertise on managing health. To provide you with the most relevant and helpful information, and understand which information is beneficial, we may combine your email and website usage information with other information we have about you. If you are a Mayo Clinic patient, this could include protected health information. If we combine this information with your protected health information, we will treat all of that information as
protected health information and will only use or disclose that information as set forth in our notice of privacy practices. You may opt-out of email communications at any time by clicking on the unsubscribe link in the e-mail.From Mayo Clinic to your inbox
Causes
Hypoglycemia occurs when your blood sugar (glucose) level falls too low for bodily functions to continue. There are several reasons why this can happen. The most common reason for low blood sugar is a side effect of medications used to treat diabetes.
Blood sugar regulation
When you eat, your body breaks down foods into glucose. Glucose, the main energy source for your body, enters the cells with the help of insulin — a hormone produced by your pancreas. Insulin allows the glucose to enter the cells and provide the fuel your cells need. Extra glucose is stored in your liver and muscles in the form of glycogen.
When you haven't eaten for several hours and your blood sugar level drops, you will stop producing insulin. Another hormone from your pancreas called glucagon signals your liver to break down the stored glycogen and release glucose into your bloodstream. This keeps your blood sugar within a standard range until you eat again.
Your body also has the ability to make glucose. This process occurs mainly in your liver, but also in your kidneys. With prolonged fasting, the body can break down fat stores and use products of fat breakdown as an alternative fuel.
Possible causes, with diabetes
If you have diabetes, you might not make insulin (type 1 diabetes) or you might be less responsive to it (type 2 diabetes). As a result, glucose builds up in the bloodstream and can reach dangerously high levels. To correct this problem, you might take insulin or other medications to lower blood sugar levels.
But too much insulin or other diabetes medications may cause your blood sugar level to drop too much, causing hypoglycemia. Hypoglycemia can also occur if you eat less than usual after taking your regular dose of diabetes medication, or if you exercise more than you typically do.
Possible causes, without diabetes
Hypoglycemia in people without diabetes is much less common. Causes can include:
- Medications. Taking someone else's oral diabetes medication accidentally is a possible cause of hypoglycemia. Other medications can cause hypoglycemia, especially in children or in people with kidney failure. One example is quinine (Qualaquin), used to treat malaria.
- Excessive alcohol drinking. Drinking heavily without eating can keep the liver from releasing glucose from its glycogen stores into the bloodstream. This can lead to hypoglycemia.
- Some critical illnesses. Severe liver illnesses such as severe hepatitis or cirrhosis, severe infection, kidney disease, and advanced heart disease can cause hypoglycemia. Kidney disorders also can keep your body from properly excreting medications. This can affect glucose levels due to a buildup of medications that lower blood sugar levels.
- Long-term starvation. Hypoglycemia can occur with malnutrition and starvation when you don't get enough food, and the glycogen stores your body needs to create glucose are used up. An eating disorder called anorexia nervosa is one example of a condition that can cause hypoglycemia and result in long-term starvation.
- Insulin overproduction. A rare tumor of the pancreas (insulinoma) can cause you to produce too much insulin, resulting in hypoglycemia. Other tumors also can result in too much production of insulin-like substances. Unusual cells of the pancreas that produce insulin can result in excessive insulin release, causing hypoglycemia.
- Hormone deficiencies. Certain adrenal gland and pituitary tumor disorders can result in an inadequate amount of certain hormones that regulate glucose production or metabolism. Children can have hypoglycemia if they have too little growth hormone.
Hypoglycemia after meals
Hypoglycemia usually occurs when you haven't eaten, but not always. Sometimes hypoglycemia symptoms occur after certain meals, but exactly why this happens is uncertain.
This type of hypoglycemia, called reactive hypoglycemia or postprandial hypoglycemia, can occur in people who have had surgeries that interfere with the usual function of the stomach. The surgery most commonly associated with this is stomach bypass surgery, but it can also occur in people who have had other surgeries.
Complications
Untreated hypoglycemia can lead to:
- Seizure
- Coma
- Death
Hypoglycemia can also cause:
- Dizziness and weakness
- Falls
- Injuries
- Motor vehicle accidents
- Greater risk of dementia in older adults
Hypoglycemia unawareness
Over time, repeated episodes of hypoglycemia can lead to hypoglycemia unawareness. The body and brain no longer produce signs and symptoms that warn of a low blood sugar, such as shakiness or irregular heartbeats (palpitations). When this happens, the risk of severe, life-threatening hypoglycemia increases.
If you have diabetes, recurring episodes of hypoglycemia and hypoglycemia unawareness, your health care provider might modify your treatment, raise your blood sugar level goals and recommend blood glucose awareness training.
A continuous glucose monitor (CGM) is an option for some people with hypoglycemia unawareness. The device can alert you when your blood sugar is too low.
Undertreated diabetes
If you have diabetes, episodes of low blood sugar are uncomfortable and can be frightening. Fear of hypoglycemia can cause you to take less insulin to ensure that your blood sugar level doesn't go too low. This can lead to uncontrolled diabetes. Talk to your health care provider about your fear, and don't change your diabetes medication dose without discussing changes with your health care provider.
Prevention
If you have diabetes
Follow the diabetes management plan you and your health care provider have developed. If you're taking new medications, changing your eating or medication schedules, or adding new exercise, talk to your health care provider about how these changes might affect your diabetes management and your risk of low blood sugar.
Learn the signs and symptoms you experience with low blood sugar. This can help you identify and treat hypoglycemia before it gets too low. Frequently checking your blood sugar level lets you know when your blood sugar is getting low.
A continuous glucose monitor (CGM) is a good option for some people. A CGM has a tiny wire that's inserted under the skin that can send blood glucose readings to a receiver. If blood sugar levels are dropping too low, some CGM models will alert you with an alarm.
Some insulin pumps are now integrated with CGMs and can shut off insulin delivery when blood sugar levels are dropping too quickly to help prevent hypoglycemia.
Be sure to always have a fast-acting carbohydrate with you, such as juice, hard candy or glucose tablets so that you can treat a falling blood sugar level before it dips dangerously low.
If you don't have diabetes
For recurring episodes of hypoglycemia, eating frequent small meals throughout the day is a stopgap measure to help prevent blood sugar levels from getting too low. However, this approach isn't advised as a long-term strategy. Work with your health care provider to identify and treat the cause of hypoglycemia.