Health Conditions A-Z Endocrine Diseases Type 1 Diabetes Signs and Symptoms of Hypoglycemia Low blood sugar can be a life-threatening situation if not treated right away. Know how to spot the signs of hypoglycemia. By Erica Meier Erica Meier Erica Meier is quality team and development editor for Health. In her role, she is a champion for those who are seeking health-related information by making jargon-laden medical knowledge available and accessible to everyone. health's editorial guidelines Published on March 6, 2023 Medically reviewed by Danielle Weiss, MD Medically reviewed by Danielle Weiss, MD Danielle Weiss, MD, FACP, is an integrative endocrinologist and founder of Center for Hormonal Health and Well-Being. learn more Share Tweet Pin Email Science Photo Library / Getty Images Hypoglycemia is a potentially dangerous condition that happens when the amount of glucose in your blood gets too low, causing symptoms such as dizziness, shakiness, lightheadedness, and a rapid heartbeat. Glucose is a type of sugar that your body needs for energy. When you eat, your body absorbs glucose and stores any extra in your muscles and your liver. The stored glucose serves as a reserve that you can tap into when you need more of this energy source in your blood. Hypoglycemia is defined as having blood glucose levels below 70 milligrams per deciliter (mg/dL). To figure out what your blood glucose number is, you have to test your blood. People with diabetes are familiar with the process of testing their blood to make sure glucose levels are not too high (hyperglycemia) or too low (hypoglycemia). Hypoglycemia is more common in people with type 1 diabetes, but people with type 2 can develop it as well. Those taking insulin (a hormone produced in the pancreas; people who have diabetes need to inject it in drug form) and some other diabetes medications need to watch out for low blood glucose levels. Low blood sugar in people without diabetes isn't common, but it's not rare either. It can happen. What you're eating, how much exercise you get, and what the weather is doing can all affect how much sugar is in your blood. Also, your risk of hypoglycemia is higher if you're older than age 65 years or have had hypoglycemia before. Health problems like kidney disease, heart disease, or cognitive impairment may increase your risk as well. Here are the signs and symptoms that will let you know if your or someone else's blood sugar is too low. Fast Heartbeat When glucose in your blood gets too low, the body recognizes that something is not right. It responds as if it were in a dangerous or stressful situation—and rightly so. If not treated immediately, hypoglycemia can be potentially life-threatening. The body's response to that potential danger is to activate the sympathoadrenal system. Specifically, the adrenal glands that sit on top of the kidneys release a hormone called norepinephrine. This gets your heart beating faster. Having a fast heartbeat allows more blood to pass through your brain and the other organs in your body. As a result, the cells can pick up more of that vital energy source that's in low supply—glucose. Shaking and Jitteriness What causes your heart to beat faster is the same thing that can also cause shaking and jitteriness. Norepinephrine isn't just a hormone, it's also a neurotransmitter, which is a chemical messenger that helps your nerves communicate with one another, helping you move, think, and generally function. As a chemical messenger, it interacts with the brain in a way that causes you to feel shaky and jittery. Nervousness and Anxiety Again, that same hormone, norepinephrine, is responsible for feelings of nervousness and anxiety. If you're starting to feel anxious, don't panic. Take a few deep breaths and check in with your body to see what else may be going on. Irritability and Confusion We need a certain level of glucose in our blood because that's how our organs get energy. When the central nervous system, which includes the brain, doesn't get enough glucose, a lot of things can happen. One of them is that behavior can change. Behavior changes can show up in different ways. You may become easily confused and may be more irritable than normal. While some degree of impatience is likely normal, aggravation or frustration that is out of character may be a sign of low blood sugar, especially if any other symptoms are present. Some people describe this sensation as "hangry," a play on words that combines "hungry" and "angry." Dizziness Low blood glucose can start to make you feel dizzy or woozy. That's because when you don't have enough glucose circulating in your blood, your brain is not getting enough, either. This lack of the brain's energy source is what generates those light-headed feelings. Be careful; feeling dizzy or woozy and experiencing hypoglycemia can cause you to faint. Fainting on its own is scary, but you can also sustain injuries such as hitting your head. Make sure to find a safe place to sit and call for assistance if you're feeling dizzy. What Are Common Causes of Dizziness? Headache Headache is another effect of your brain not having enough glucose. The cells in your brain work all day long, and they need lots of glucose to do their job. In fact, even though your brain is only about 2% of your body weight, it is your main consumer of glucose. Hunger Speaking of hanger, hunger is also a symptom of low blood sugar. It makes perfect sense for your body to get hungry, too. Eating, especially foods with carbohydrates, drives up blood glucose levels. Your blood will release acetylcholine in response to hypoglycemia. Acetylcholine is a neurotransmitter. It tells your brain to activate the circuits that make you feel hungry. Luckily, grabbing a snack or a quick bite should help you feel better. People with diabetes know not to eat too much if their blood glucose is low. Often, they follow the "15-15 Rule," which means having 15 grams of carbohydrates and then waiting 15 minutes to see if their blood glucose has gone up. Tiredness This symptom is also the result of the central nervous system not getting enough glucose from the bloodstream. When your brain is deprived of this key energy source, it's not uncommon to feel drained. If you're feeling more tired than normal and have other symptoms, a simple blood glucose test can let you know if low glucose is the cause. Difficulty Speaking Speaking is controlled in the brain. If your brain is not getting the energy it needs to function, speech may suffer as a result. As a word of caution, difficulties speaking can also be a sign of other neurological conditions, including a stroke. Make sure you know how to spot a stroke so you can tell it apart from hypoglycemia. Sweating Another sign that blood glucose levels are getting low is sweating. Sweating is also caused by the release of acetylcholine. Sweating that is more excessive than normal and is accompanied by any of these other symptoms may tip you off to low blood sugar. Sweating can happen during the day, but it can also happen at night in your sleep. Poor Sleep Quality When you're sleeping, your blood glucose can get low and stay low for hours. It's not good when this happens because a number of problems can occur. Whether you notice them or someone sleeping near you does, these symptoms can happen while you're asleep: Crying out during sleepHaving nightmaresWaking up sweaty with damp pajamas and bedsheetsFeeling tired, irritable, or confused in the morning upon waking What To Know About Sleep Deprivation, and How it Can Affect Your Health Severe Symptoms From the above signs and symptoms, you may have noticed that your body goes into a sort of crisis-response mode if your blood glucose levels drop too low. There is a very good reason for this: Hypoglycemia can be very dangerous and needs to be treated right away. If blood glucose drops below 54 milligrams per deciliter it is severely low. With levels that low, the brain isn't getting nearly enough fuel. This can cause you to have problems walking or seeing clearly. If deprived of fuel long enough, the brain may stop working. In extreme situations, loss of consciousness or seizure can occur. Blood glucose can even get so low it can cause death. When To See a Healthcare Provider Symptoms of hypoglycemia need to be treated immediately. If you're experiencing these symptoms and think you may have low blood glucose, talk to a healthcare provider. Once you determine what's causing your low glucose levels, you can work out a treatment plan. If you have diabetes, especially if you're taking insulin or certain other diabetes medications, you probably know the importance of having glucose sources on you at all times. Fruit juices are a good source of readily available carbohydrates. Glucose gel, glucose tablets, and hard candy are also effective. If these fixes aren't keeping your blood glucose levels high enough, you may need glucagon. Glucagon is a hormone that healthcare providers can prescribe to treat severely low blood glucose. If your blood glucose is persistently low, your healthcare provider may even prescribe an emergency glucagon kit that you can keep with you. 5 Factors That Affect How Often To Check Your Blood Sugar A Quick Review Low blood sugar needs to be treated immediately. Signs and symptoms of hypoglycemia must be taken very seriously. This condition can be deadly if it is not treated right away. Be aware of hypoglycemia unawareness. This is when you have symptoms but fail to recognize them. If you don't notice the symptoms when they start, your blood glucose can drop dangerously low. If you're at risk of hypoglycemia, especially if you don't easily recognize the symptoms, get into a habit of checking your blood glucose often. You may want to test your levels in certain situations, too, like before you get behind the wheel. Also, see a healthcare provider if you're experiencing low blood sugar on a regular basis so you can get the right treatment for your unique needs. Was this page helpful? Thanks for your feedback! Tell us why! Other Submit 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. MedlinePlus. Hypoglycemia. Centers for Disease Control and Prevention. Low blood sugar (hypoglycemia). National Institute of Diabetes and Digestive and Kidney Diseases. Low blood glucose (hypoglycemia). Mathew P, Thoppil D. Hypoglycemia. In: StatPearls. StatPearls Publishing; 2022. Nakhleh A, Shehadeh N. Hypoglycemia in diabetes: An update on pathophysiology, treatment, and prevention. World J Diabetes. 2021;12(12):2036-2049. doi:10.4239/wjd.v12.i12.2036 Mergenthaler P, Lindauer U, Dienel GA, Meisel A. Sugar for the brain: the role of glucose in physiological and pathological brain function. Trends Neurosci. 2013;36(10):587-597. doi:10.1016/j.tins.2013.07.001 American Diabetes Association. 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