Low Blood Sugar Symptoms: Signs, Levels and What to Do
Common signs of low blood sugar are a fast heartbeat, shaking, sweating, nervousness, irritability or confusion, dizziness and hunger. A low is a glucose reading below 70 mg/dL (3.9 mmol/L). If you can, check your blood sugar and treat right away.
Symptoms of a low
| Stage | What people notice | Source |
|---|---|---|
| Early | Fast heartbeat, shaking or jitteriness, sweating, nervousness or anxiety, hunger, tiredness, headache, dizziness or lightheadedness, irritability | CDC, NIDDK |
| Getting worse | Confusion, trouble seeing clearly or speaking clearly, weakness, trouble walking, acting strangely | CDC, NIDDK |
| Very low | Seizure, fainting or loss of consciousness | CDC, NIDDK |
Not everyone has the same signs, and signs can differ from one low to the next. Ask your care team what yours look like, and tell the people around you.
The ADA levels of low
- Level 1: below 70 mg/dL (3.9 mmol/L) and at least 54 mg/dL (3.0 mmol/L).
- Level 2: below 54 mg/dL (3.0 mmol/L). The CDC calls this severe.
- Level 3: a severe event with altered mental or physical status that needs another person’s help, at any glucose.
The CDC says that below 70 mg/dL you need to act to bring it back up. For a CGM user, the ADA goal is under 4% of the time below 70 and under 1% below 54. See the blood sugar chart and the blood sugar of 60 page.
If you cannot feel your lows
Repeated lows can blunt the early warning signs, so a person may go from feeling fine to confused with little warning. Tell your care team if you have a low you did not feel, or if lows are becoming more frequent. They can review your plan. A CGM with alarms is one tool clinicians use, and glucagon is another (see glucagon). The ADA recommends it for everyone taking insulin or at high risk of lows.
What to do
- Check your blood sugar if you can. If you cannot check, ask your care team in advance what to do.
- Eat or drink 15 to 20 grams of fast-acting carbohydrate. The NIDDK lists four glucose tablets, half a cup of juice or half a can of regular soda. The rule of 15 has the steps, and glucose tablets explains the easiest option to carry.
- Recheck in 15 minutes and repeat if still low.
- Tell your care team about any low, especially if it was severe or came without warning.
Frequently asked questions
What are the first signs of low blood sugar?
The CDC lists a fast heartbeat, shaking, sweating, nervousness or anxiety, irritability or confusion, dizziness and hunger. The NIDDK adds feeling tired, a headache, and not being able to see or speak clearly.
What blood sugar level counts as low?
Below 70 mg/dL (3.9 mmol/L). The ADA calls 54 to 69 mg/dL level 1 and below 54 mg/dL (3.0 mmol/L) level 2. The CDC calls below 54 severe because someone else may need to help. Your care team may give you a different line.
Can I have low blood sugar without symptoms?
Yes. Some people stop feeling the early warning signs of a low, which clinicians call hypoglycemia unawareness. A meter or CGM may be the only warning. Tell your care team if this happens.
Is low blood sugar an emergency?
It can be. If someone is unalert, passes out, has a seizure or cannot swallow safely, call 911. Otherwise, treat a low right away with fast-acting carbohydrate, as in the rule of 15.
Can low blood sugar happen if I do not have diabetes?
It can, though it is less common. If you have symptoms like these with a low reading, or often, talk to a clinician. This page does not diagnose.
Information only, not medical advice. Your care team may set different targets for you, and only a lab test ordered by a clinician can diagnose diabetes or prediabetes. See our medical disclaimer.
Sources
- CDC: Low Blood Sugar (Hypoglycemia) symptoms
- NIDDK: Low Blood Glucose (Hypoglycemia)
- ADA Standards of Care in Diabetes—2026, Section 6: Glycemic Goals, Hypoglycemia, and Hyperglycemic Crises
Last reviewed: by the Diabetes Blogs editorial team. Information only, not medical advice.
