Hypoglycemia, or low blood sugar, happens when glucose levels drop below what the body needs to function normally, most often in people being treated for diabetes but occasionally in others as well. Recognizing the symptoms quickly matters, because untreated low blood sugar can progress from mild to dangerous within a short time.
Early Warning Signs
- Shakiness or trembling
- Sweating, often sudden and out of proportion to activity or temperature
- Rapid heartbeat
- Sudden hunger
- Irritability or anxiety
- Dizziness or lightheadedness
More Severe Symptoms
If blood sugar continues to drop, symptoms can progress to confusion, blurred vision, slurred speech, difficulty concentrating, and in severe cases, loss of consciousness or seizures. Severe hypoglycemia is a medical emergency.
Who’s Most at Risk
- People with diabetes taking insulin or certain oral medications, especially after a missed meal or extra exercise
- People who drink alcohol without eating enough, since alcohol can interfere with the liver’s glucose release
- Those who’ve had certain weight-loss or stomach surgeries, which can affect how quickly sugar is absorbed
- Rarely, people with certain hormone or tumor conditions affecting insulin production
The 15-15 Rule
A common first step for mild to moderate hypoglycemia is the “15-15 rule”: consume about 15 grams of fast-acting carbohydrate, such as glucose tablets, juice, or regular soda, then recheck blood sugar after 15 minutes, repeating if it’s still low.
Fast-Acting Carbohydrate Options
- Glucose tablets or gel, which act predictably and are easy to dose
- Half a cup of fruit juice or regular soda
- A tablespoon of honey or sugar
- Hard candies, in a measured amount
Why It Matters to Treat It Quickly
The brain depends heavily on a steady glucose supply, so even moderate hypoglycemia can impair judgment and coordination quickly, which is part of why driving or operating machinery during a low blood sugar episode is strongly discouraged.
Preventing Repeated Episodes
For people with diabetes, frequent lows are often a sign that medication timing, dosing, or meal planning needs adjustment, which is worth reviewing with a healthcare provider rather than simply treating each episode as it comes.
Nighttime Hypoglycemia
Low blood sugar can also happen during sleep, sometimes showing up as night sweats, nightmares, or waking up with a headache and feeling unusually tired, even without the person noticing the episode itself. Continuous glucose monitors have made these overnight patterns easier to detect for people managing diabetes.
Carrying Emergency Supplies
People prone to frequent lows, particularly those on insulin, are often advised to carry fast-acting carbohydrate sources with them, along with a glucagon emergency kit if prescribed, so they’re prepared even outside the home.
Hypoglycemia Unawareness
Some people, particularly those who’ve had diabetes for many years or who experience frequent lows, can develop reduced ability to feel the early warning symptoms, a condition called hypoglycemia unawareness. This makes regular blood sugar checks or continuous glucose monitoring especially important, since relying on symptoms alone may not catch a low in time.
Telling Family and Coworkers
Letting close family members, coworkers, or roommates know the basic signs of a low and how to help, such as offering juice or calling for help if someone seems confused, can add an extra layer of safety, especially for those prone to more severe episodes.
Related Reading
Low blood sugar symptoms can sometimes be confused with other conditions, so it’s worth also reading about the difference between type 1 and type 2 diabetes and signs of dehydration in adults, which can present with overlapping symptoms.
For more detail, see the NIDDK’s guide to hypoglycemia.
Frequently Asked Questions
Can hypoglycemia happen in people without diabetes?
It’s uncommon, but it can occur after very intense exercise, heavy drinking without food, or in rare cases, certain medical conditions affecting insulin regulation.
What blood sugar level counts as hypoglycemia?
For most people with diabetes, a reading below 70 mg/dL is considered low, though individual targets can vary and should be set with a healthcare provider.
Should you eat a full meal to treat a low?
Fast-acting carbs are better for immediate treatment; a full meal can be eaten afterward once blood sugar has stabilized, especially if a meal was already due.
Is it safe to exercise after treating a low blood sugar episode?
It’s generally best to wait until blood sugar has stabilized and symptoms have fully resolved before resuming exercise.
This is general information, not medical advice. See a doctor for personal guidance or before making changes to your health routine.
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