Medically Reviewed

Hypoglycemia: 9 Signs of Low Blood Sugar

You know that feeling of irritation and sluggishness that appears around 3 p.m., on days when you've skipped breakfast and barely touched your lunch? Your friends may call it feeling "hangry," but it's actually a medical condition, known as hypoglycemia (low blood sugar), which is defined as blood glucose below 70mg/dL, according to the American Diabetes Association. While mostly it's just an uncomfortable feeling that can be remedied by food, if you have repeated episodes of hypoglycemia, or if your sugar level is chronically too low, there may be other causes for hypoglycemia that require you to take action to avoid serious problems. How do you know if you have hypoglycemia? Look for these signs.


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You Feel Like You Might Pass Out

If you suddenly feel weak, shaky, or lightheaded—or if you even faint—you could be experiencing hypoglycemia, per the Mayo Clinic. A headache that comes on quickly, weakness or tremor in your arms or legs, and a slight trembling of your body are also signs your blood sugar is too low. Sometimes, these symptoms are also tied to low blood pressure. To get back to a more normal sugar level, eat something with sugar, such as pure glucose in the form of tablets or gel, for example. If it’s not urgent (you don’t have diabetes), go to the carbohydrates.


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You Feel Super Hungry

Back to that “hangry” feeling—that intense hunger with low blood sugar that makes you feel a bit crazed. Ginger Vieira, 33, who has type 1 diabetes, says “severe lows can make you want to eat everything in sight.” The reason? Counter-regulatory hormones known as glucagon, cortisol, and adrenaline, says Siripoom McKay, M.D., assistant professor of pediatrics, diabetes, and endocrinology at Baylor College of Medicine in Houston, TX. When you're hypoglycemic, these chemicals surge to counteract insulin and get your blood sugar back up. In the meantime, they can make you feel like you’ll starve if you don’t eat all the food—immediately.


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You're Clammy and Sweaty

With hypoglycemia, you may find that you break out in a cold sweat even though you’re not overheated, and you may get pale and feel clammy, even though you're not physically exerting yourself. This happens because low blood-sugar levels trigger the body’s fight or flight response, leading to a stress response and the release of adrenaline, a hormone. This adrenaline burst causes sweating along with other symptoms. Symptoms of type 1 diabetes can include feeling damp and sticky from hypoglycemia at intervals throughout a given week.


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Your Heart Is Racing

The extra adrenaline released during hypoglycemia can also cause an anxious feeling tied to your heart to beating fast as well as an irregular heart beat or heart palpitations, which you may feel as a pounding sensation in your chest. Johnson says he’s used to feeling his heart racing when his blood sugar is low. A caution from Betul Hatipoglu, M.D., director of the Case Center for Diabetes, Obesity and Metabolism at Case Western Reserve University in Cleveland, OH: Take extra care to properly treat any form of heart disease, since the added effect of a fast or irregular heartbeat with hypoglycemia can make both conditions worse.


You Feel Confused and Out of Sorts

With hypoglycemia, all of your cells hunger for fuel, including your brain, says Kathleen Wyne, M.D., Ph.D., director of the Ohio State University Adult Type 1 Diabetes Program in Columbus. As a result, a risk with hypoglycemia is that you may feel spacey and confused, and you may have trouble communicating. With diabetes, ask friends and family to stay alert and ask questions like, “Are you struggling to talk right now?” advises Janet G. Zappe, R.N., a clinical program manager for the Diabetes Research Center at The Ohio State University Wexner Medical Center. It's always good to keep low blood-sugar snacks on hand as well.


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You're Making Mistakes Left and Right

Keep screwing things up? Maybe you’ve made a computer error. A speaking error. A calculation error. You can’t seem to get back on track. Stop whatever you're doing to regroup and consider that hypoglycemia might be to blame: A recent study in Diabetes Care found impaired cognitive function in people with low blood sugar. Says Dr. Wyne, “A dramatic example of this is getting in your car and driving somewhere, then an hour or two later not knowing how you got there. Even if you realize your levels are low, you may not be able to think clearly enough to do something correctly.”


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You're Extra Irritated and Angry

Is your level of frustration a 20 out of 10? Anger and anxiety are tied to diabetes and hypoglycemia, according to the Centers for Disease Control and Prevention. “The most common mood changes are being belligerent and argumentative,” says Dr. Wyne. “Or it could be more subtle in just refusing to discuss something or not agreeing to something that is normally acceptable to you,” she says. If your partner tells you you’re crankier than usual, take note. Personality changes are a major sign of hypoglycemia, agrees Zappe.


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You Feel Anxious and Unsettled

Extremely low blood sugar can cause anxiety because the brain isn’t getting enough fuel and you may fear what happens next. Johnson knows it’s time to check his glucose when these sensations start to creep up. Diagnosed and treated for type 1 diabetes starting when he was age 5, he’s used to the anxiety bubbling up, but isn’t always successful at keeping the feelings at bay. “I work hard to manage my blood sugars, but diabetes is complicated and the tools we have are no match for a fully functioning endocrine system that can regulate things naturally,” he says.


You Feel Suddenly Tired or Sleepy

Diabetes fatigue is a real complication of the disease. If you have diabetes and suddenly feel tired, or overwhelmingly sleepy, it can be a sign that your blood sugar is low, and your body is not getting enough energy. Rather than taking a nap—and the risk that your hypoglycemia episode will worsen–eat something, drink that juice, take your glucose tablets or gel. This isn't a time to lie down and go to sleep, no matter how much you may want to.


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What to Do

With hypoglycemia, time is of the essence. Eat foods that deliver sugar quickly, and you’ll feel much better. And if you have diabetes, turbo-charge your preparations given that an extreme blood-sugar drop that can happen. A study published in the Indian Journal of Endocrinology and Metabolism said that “acute interruption” of glucose supply to the brain could result in functional brain failure and coma or death; we have four minutes to treat before brain cells start dying. Yep, that's totally scary, but it's also crucial information to know. With diabetes emergencies, a rescue medication called glucagon (a hormone) can be used to turn things around. Ask your doctor if it's right for you.


This article was originally published May 10, 2013 and most recently updated January 3, 2024.