Low blood sugar with diabetes: symptoms and what to do during a low

What is low blood sugar (hypoglycemia)?

Low blood sugar, or hypoglycemia, is blood sugar below 70 mg/dL, and ADA sorts it into three levels.^[1][2] Level 1 is below 70 and at or above 54 mg/dL. Level 2 is below 54 mg/dL. Level 3 is any severe episode in which someone needs help from another person to recover, whatever the reading.^[1]

Lows mainly affect people who take insulin, sulfonylureas or meglitinides. ADA notes that clinically significant lows are rare with other diabetes medicines.^[1] CDC notes that lows are especially common in type 1 diabetes and can happen even when blood sugar is managed closely.^[2]

This guide covers how to recognize a low, what to do during one, when it is an emergency and what to tell your care team afterwards. It does not cover adjusting your medicines, which is a conversation for your care team.

What are the symptoms of low blood sugar?

The common symptoms of low blood sugar are a fast heartbeat, shaking, sweating, nervousness or anxiety, irritability or confusion, dizziness and hunger.^[2] As a low gets worse, CDC lists feeling weak, trouble walking or seeing clearly, acting strangely or feeling confused, and seizures.^[2] Below 54 mg/dL, a person may faint and often needs someone else's help.^[2]

Some people have no symptoms when their blood sugar is low. This is called hypoglycemia unawareness. CDC notes it is more likely if you have had diabetes for more than 5 to 10 years, often have lows, or take certain medicines such as beta blockers.^[2] ADA suggests a simple question for care teams to ask: "Can you always feel when your blood glucose is low?"^[1] If your honest answer is no, it is worth raising at your next appointment. CDC notes that checking matters most before driving or being active.^[2]

What do I do during a hypoglycemia episode?

CDC's 15-15 rule is the standard first response: have 15 grams of fast-acting carbohydrate, wait 15 minutes and check again.^[3]

1. Check your blood sugar if you can.
2. Have 15 grams of fast-acting carbohydrate. CDC's examples are 4 ounces (half a cup) of juice or regular soda, 1 tablespoon of sugar, honey or syrup, or glucose tablets or gel used as the label directs.^[3]
3. Wait 15 minutes and check again.
4. If you are still below 70 mg/dL, repeat the steps.^[3]
5. Once your blood sugar is back in range, eat a balanced snack or meal with protein and carbohydrates.^[3]

ADA prefers pure glucose for the first treatment and advises avoiding foods high in fat or protein at that stage, because they slow and prolong the rise.^[1] People who take acarbose are advised to use pure glucose only.^[1] If you use an automated insulin delivery system, ADA notes the usual amount may be smaller, so ask your care team what yours is.^[1] CDC notes that young children may need less than 15 grams.^[3]

Step 5 matters because insulin or some tablets may still be working after the first recovery, and ADA notes that lows can come back unless more food is eaten.^[1]

When is low blood sugar an emergency?

Low blood sugar is an emergency when a person is not alert, cannot be woken, has a seizure or cannot swallow safely. ADA's standards say emergency services are called for anyone who is not alert or cannot take carbohydrates by mouth.^[1]

• Call 911.
• Do not give food or drink to someone who is not alert. ADA describes giving oral glucose only to an alert person.^[1]
• Use glucagon if it has been prescribed. ADA recommends glucagon for everyone who takes insulin or is at high risk of lows, and prefers ready-to-use nasal and injectable forms because they are easier to give.^[1]
• Never give insulin to someone having a low.^[1]
• CDC advises contacting a doctor for emergency treatment right after a glucagon injection.^[3]

ADA recommends that family members, roommates, coworkers and others close to you know where your glucagon is kept and how to use it.^[1] ADA's severe hypoglycemia page covers the supplies to keep on hand. You might say: "If I'm confused and can't swallow, use the glucagon in my bag and call 911." This is an illustrative prompt, not a quote from a real patient. Use your own words.

Why do lows happen, including at night?

Lows happen when glucose-lowering medicine meets less food, more activity or something else that lowers blood sugar. CDC lists taking too much insulin, not eating enough carbohydrates for the insulin taken, the timing of insulin, the amount and timing of physical activity, alcohol, hot and humid weather, unexpected schedule changes, high altitude, puberty and menstruation.^[2] ADA adds fasting, delayed meals and illness.^[1] ADA's page on the causes and prevention of low blood glucose goes into more detail.

CDC describes nighttime lows following an active day, activity close to bedtime, too much insulin, or alcohol at night. You may wake up during a low, but CDC advises against relying on that, and notes that a CGM can alert you if your blood sugar drops while you sleep.^[2] ADA advises care teams to compare sensor and meter readings with symptoms, because a low sensor reading with no symptoms can sometimes come from pressure on the sensor during sleep.^[1]

If you fast for religious or cultural reasons, ADA asks care teams to plan your treatment around it with you.^[1] For medicines that are timed with meals, read when to take diabetes medicines.

What can I tell my care team after a low?

Tell your care team when it happened, what your reading was, what came before it and how you treated it. ADA recommends reviewing lows at every visit for people at risk, and says one or more level 2 or level 3 lows is a reason to reevaluate the treatment plan, including changing or reducing medicines where appropriate.^[1] ADA also recommends asking people at high risk about fear of lows at least once a year.^[1]

You might say: "I had two lows last week after evening walks. Can we look at whether my plan needs to change?" This is an illustrative prompt, not a quote from a real patient. Use your own words and choose how much you want to share.

Where can I find support with lows?

The right support depends on whether you need a clearer plan for lows, training for the people around you, or help with the worry lows can bring. Compare diabetes resources to see what each service offers and where it is available. Explore diabetes patient questions for illustrative ways to describe what happened. The mama health app is one place to ask about your condition and get answers grounded in medical science and the experience of others living with diabetes. Learn more about its diabetes support.