Low blood sugar, or hypoglycemia, is usually a reading below 70 mg/dL, and the severe range starts at 55 mg/dL or lower. Call 911 if the person is unconscious, is having a seizure or fainting, or does not improve with treatment. For someone who is awake and able to swallow with mild or moderate symptoms, the usual first step is fast-acting carbohydrate and a recheck after 15 minutes.
When to call 911 for low blood sugar
As of October 14, 2026, the UC Davis Health hypoglycemia page lists these emergency symptoms. Call 911 when they do not improve with emergency treatment:
- Extreme weakness or tiredness
- Fainting or loss of consciousness
- Seizure or sudden, uncontrollable movements
- Severe confusion
- Slurred speech
The Harvard Health Publishing hypoglycemia page says to call for emergency medical help whenever someone is unconscious or disoriented enough that they cannot safely be treated by mouth. MedlinePlus adds that severe insulin reactions can be fatal, so treatment should start right away.
The American Association of Clinical Endocrinologists page ’11 Things You Need to Know About Low Blood Sugar’, captured October 14, 2026, says to summon help if blood sugar does not rise after two tries of treatment.
What makes a low blood sugar episode severe?
The sources agree on the general lines but do not set one number for everyone. UC Davis Health says the ideal level depends on age and health conditions, and that your care team can tell you what is healthy for you.
| Situation | What the sources say | What it means for you |
|---|---|---|
| Below 70 mg/dL | UC Davis Health says this is usually considered low. | Treat it as a low and follow your care plan. |
| Below 55 mg/dL | UC Davis Health says levels below 55 mg/dL can be life-threatening. Healthline says the American Diabetes Association calls severe hypoglycemia a medical emergency at this level and below. | Treat this as the severe range and watch for emergency signs. |
| Awake but cannot eat or drink fast-acting carbohydrate | UC Davis Health counts this as severe. | Call for emergency help. |
| Unresponsive, unconscious, or having a seizure | UC Davis Health and Harvard Health place this in the emergency range. | Call 911 now. Harvard Health says an unconscious patient is treated with glucagon or intravenous glucose by emergency responders or in a hospital. |
Treating a conscious low at home versus a severe event
UC Davis Health says that if you have mild to moderate symptoms, you can eat or drink fast-acting carbohydrate, then check again after 15 minutes and repeat if your level is still low. Harvard Health says symptoms in a conscious person usually go away within five to 15 minutes after taking something sweet. For lows caused by sulfonylureas or long-acting insulin, which can come back, Harvard Health suggests a longer-lasting carbohydrate after the fast one.
| Feature | Awake and able to swallow | Severe event |
|---|---|---|
| Typical signs | Shaky, sweaty, hungry, dizzy, irritable, headache, racing heartbeat (UC Davis Health list) | Fainting, seizure, severe confusion, slurred speech, unresponsiveness |
| First step | Fast-acting carbohydrate, then recheck after 15 minutes | Call 911 and tell the people with you what you know |
| Who handles it | You, with your care team’s plan | Emergency responders or a trained person (Harvard Health Publishing, captured October 14, 2026, says a knowledgeable family member or friend may give glucagon if a hypoglycemic patient is unconscious and cannot safely take sugar by mouth) |
What is the 15-15 rule, and can I get a PDF?
This page does not include a downloadable PDF, but the steps are short enough to save or print from this section. Healthline describes the American Diabetes Association’s 15-15 approach this way:
- If your blood sugar is below 70 mg/dL, take a fast-acting carbohydrate.
- Wait 15 minutes and check again.
- If it is still 70 mg/dL or lower, take another fast-acting carbohydrate and recheck after 15 minutes.
The American Association of Clinical Endocrinologists page ’11 Things You Need to Know About Low Blood Sugar’, captured October 14, 2026, adds that once blood sugar is back to normal, you should eat a meal or snack so it does not drop again.
Healthline notes that the amount of carbohydrate needed can differ from person to person, so ask your care team what amount fits you.
What should I eat when blood sugar is low?
UC Davis Health lists crackers, juice, soda, sugar, honey, syrup and hard candy as fast-acting carbohydrates, and says glucose tablets or gels sold over the counter also contain them.
Is peanut butter good for hypoglycemia?
Healthline suggests peanut butter or other nut butter without added sugar, eaten with crackers, when your reading is above 70 mg/dL but trending down. In that article, the crackers raise blood sugar gradually while the protein and fat help it last. It is a slower option, so for a reading that is already low, the fast-acting carbohydrates above come first.
What causes low blood sugar, and what can I do to help prevent it?
UC Davis Health lists skipping meals or eating less than usual, intense or new exercise, excessive alcohol use, too much insulin, and hormone, liver or kidney problems as causes. MedlinePlus lists medicines that can lower blood sugar, including insulin, sulfonylureas, glinides and SGLT2 inhibitors. Harvard Health notes that alcohol can cause serious lows even hours after insulin was taken.
UC Davis Health suggests checking your level often, eating or drinking something with carbohydrate before exercise, making sure family and friends know what to do, and keeping a diary of levels, food, medicines and activity. Ask your clinician which of your medicines can cause lows, and ask before changing any medicine. Our guide on how often to check blood sugar can help you plan checks.
Can I feel a low coming on?
UC Davis Health says symptoms can start suddenly and get worse as blood sugar drops. Some people who often have lows, or who have type 1 diabetes, may have no noticeable symptoms. Harvard Health says people with long-standing diabetes can lose the early warning signs, which it calls hypoglycemic unawareness and describes as very serious. Read more in our page on dangerous blood sugar levels and signs.
What these guidelines cannot tell you
These pages give general lines, not your personal target, and they cannot tell you the cause of your lows or which medicine is involved. Use this page to decide when to call for help, and bring your own numbers to your clinician for your treatment plan.
Your next step
Before your next visit, write down each low: the time, the reading if you have one, what you ate or did, what you took, and how you felt. Our guide to building a symptom timeline for a primary care visit shows how to organize it. If you have urgent symptoms, call 911 first, then read our guide to which contact route to use for urgent symptoms.
By the Primary Care Visit Guide Team
This article is for general information purposes only and does not constitute medical advice. Consult your doctor or qualified healthcare provider before making changes to your health routine.
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