Hypoglycemia (low blood glucose), sometimes called an “insulin reaction,” is often defined for people with diabetes as a blood glucose level below 70 mg/dL. Some people start feeling symptoms in the 60–70 range, while others may not notice symptoms until it’s lower, and some whose glucose has been high for months or years may experience symptoms in the 100 to 120 mg/dL range. Recognizing hypoglycemia symptoms early helps you treat it sooner—before a mild low becomes a bigger problem.
This page highlights hypoglycemia symptoms and how they can appear in daily life, including nighttime signs. For a step-by-step plan to treat a low, see the treatment page.
Series navigation: Hypoglycemia Overview | Symptoms | Prevention | Treatment | Hypoglycemia Unawareness| Staying Calm When Assisting Someone
What does low blood sugar feel like?
Low blood sugar symptoms vary from person to person. You might experience a clear warning sign, such as shaking, or suddenly notice several symptoms all at once. Symptoms can also differ from one low to the next in the same individual.
Two “types” of symptoms (why lows feel so strange)
Symptoms come from two main effects:
- Stress hormone effects(your body releases hormones to raise glucose). These often cause shakiness, sweating, and a racing heart.
- Brain low (“neuroglycopenic”) effects occur when the brain lacks enough glucose. These often cause confusion, poor concentration, and slower reaction times.
When your brain has low glucose levels, you might not accurately assess how impaired you are. That’s why family members sometimes notice symptoms before you do.
Why do symptoms of hypoglycemia differ so much?
Symptoms vary due to differences in:
- How quickly glucose drops (a rapid decrease can feel more intense)
- Your recent pattern of lows(repeated lows can dull warning signs)
- Sleep(nighttime lows are more difficult to detect)
- Age, medications, and other health conditions
- Using a CGMand your alert settings
If you’ve experienced a significant low recently, your usual warning signs (like sweating or shaking) might be less noticeable for a while. If that sounds familiar, check out the dedicated page on hypoglycemia unawareness.
Which diabetes medications can lead to symptoms of low blood sugar?
Low blood sugars can occur whenever insulin is used. Less commonly, hypoglycemia can also happen with some type 2 diabetes pills that increase insulin release, especially:
- Sulfonylureas (for example, chlorpropamide/Diabinese, glyburide, glipizide)
- Meglitinides (for example, nateglinide and Starlix)
If you use these medications and experience lows, contact your clinician promptly—some lows can last longer with certain pills, and prevention strategies may vary. Note that GLP-1 and SGLT2 medications, and pioglitazone, do not directly cause hypoglycemia.
What are the most common symptoms of hypoglycemia?
Below is a practical list you can quickly scan. If you notice any of these and you’re at risk for hypoglycemia, check your glucose (meter or CGM) and treat if you’re low.
Common early warning signs
- Shaking or tremor
- Sweating, chills, clamminess
- Fast heart rate or palpitations
- Hunger
- Anxiety, nervousness, or a feeling of a “sense of doom”
- Tingling sensation (sometimes around the mouth)
- Headache
- Pale appearance
“Brain low” symptoms (take these seriously)
- Dizziness or feeling lightheaded
- Blurred vision
- Confusion, difficulty concentrating, or trouble finding words
- Clumsiness or delayed reaction time
- Irritability, sudden mood swings, or unusual behavior
- Sudden tiredness or weakness
- Nausea, sometimes accompanied by vomiting
Severe symptoms that indicate an emergency risk
- Seizure
- Loss of consciousness
If a person is unconscious, having a seizure, or cannot swallow safely, it is a medical emergency. Use glucagon if available and call emergency services. For details, see the treatment page.
Series navigation: Hypoglycemia Overview | Symptoms | Prevention | Treatment | Hypoglycemia Unawareness| Staying Calm When Assisting Someone
Other Resources
- Healthlinecreated a great infographic showing the effects of low blood sugar. Take a look.
- American Diabetes Association (ADA): Low Blood Glucose (Hypoglycemia)
- CDC: Low Blood Sugar (Hypoglycemia)
- Diabetes Care (ADA Standards of Care)
- Mayo Clinic: Hypoglycemia overview
Medical disclaimer: This content is for education and does not replace individualized medical advice. Seek urgent help for severe lows (seizure, unconsciousness, or inability to swallow safely), and talk with your clinician if you’re having frequent or unexplained hypoglycemia.
Last Updated on December 29, 2025