Hypoglycemia (low blood sugar), sometimes called an “insulin reaction,” is often defined for people with diabetes as a glucose level below 70 mg/dL. Some people begin feeling symptoms in the 60–70 range, while others may not notice symptoms until lower. Recognizing hypoglycemia symptoms early helps you treat sooner—before a mild low becomes a bigger problem.
This page focuses on hypoglycemia symptoms and how they can show up in everyday life, including nighttime clues. For the step-by-step plan to treat a low, visit the treatment page.
Series navigation: Hypoglycemia Overview | Symptoms | Prevention | Treatment | Hypoglycemia Unawareness| Emotion Control With Lows
What does low blood sugar feel like?
Low blood sugar symptoms are different for everyone. You might feel one clear warning sign (like shaking), or you may suddenly notice several symptoms at once. Symptoms can also vary from one low to the next in the same person.
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 when the brain doesn’t have enough glucose. These often cause confusion, poor concentration, and slower reaction time.
When your brain is low on glucose, you may not accurately judge how impaired you are. That’s why family members sometimes notice symptoms before you do.
Why do hypoglycemia symptoms vary so much?
Symptoms vary because of differences in:
- How fast glucose is dropping (a fast drop can feel more dramatic)
- Your recent history of lows (repeated lows can blunt warning symptoms)
- Sleep (nighttime lows can be harder to detect)
- Age, medications, and other medical conditions
- Use of a CGM and your alert settings
If you’ve had a significant low recently, your usual warning signs (like sweating or shaking) may be weaker for a period of time. If that sounds familiar, read the dedicated page on hypoglycemia unawareness.
Which diabetes medications can cause low blood sugar symptoms?
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/Starlix)
If you use these medications and you’re having lows, contact your clinician promptly—some lows can last longer with certain pills, and prevention strategies may differ.
What are the most common hypoglycemia symptoms?
Below is a practical list you can scan quickly. 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 “sense of doom”
- Tingling (sometimes around the mouth)
- Headache
- Pale appearance
“Brain low” symptoms (take these seriously)
- Dizziness or lightheadedness
- Blurred vision
- Confusion, poor concentration, or trouble finding words
- Clumsiness or slowed reaction time
- Irritability, sudden mood change, or unusual behavior
- Sudden tiredness or weakness
- Nausea (sometimes vomiting)
Severe symptoms (emergency risk)
- Seizure
- Loss of consciousness
If a person is unconscious, having a seizure, or cannot swallow safely, this 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| Emotion Control With Lows
Other Resources
- Healthline created a great infographic that shows the effects of a 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.
Diabetes Response Service – the only scheduled proactive self-management Personal Call System using live operators to monitor, alert and prevent severe diabetic hypoglycemia.
Last Updated on December 18, 2025