Low blood sugar, also called hypoglycemia, is one of the most important short-term complications people with diabetes should know how to recognize and treat. It is particularly relevant for people using insulin or certain diabetes medicines that increase insulin release.
For most people with diabetes, a glucose level below 70 mg/dL (3.9 mmol/L) is considered clinically important. The American Diabetes Association (ADA) classifies level 1 hypoglycemia as 54–69 mg/dL, level 2 as below 54 mg/dL, and level 3 as a severe event in which a person needs help from another person to recover.
What Is Low Blood Sugar in Diabetes?
Low blood sugar occurs when glucose falls below the level needed to safely support normal body function. Symptoms can develop quickly and may include sweating, shaking, hunger, palpitations, dizziness, irritability, difficulty concentrating or confusion.
Very low blood sugar can affect brain function and may cause seizures, loss of consciousness or other serious complications. Repeated episodes can also contribute to hypoglycemia unawareness, where a person no longer notices the warning symptoms reliably.
What Blood Sugar Level Is Considered Low?
- Below 70 mg/dL: clinically important hypoglycemia and should prompt treatment.
- Below 54 mg/dL: level 2 hypoglycemia and requires immediate action.
- Level 3 hypoglycemia: severe hypoglycemia requiring assistance from another person, regardless of the exact glucose number.
People using a continuous glucose monitor (CGM) should also pay attention to time spent below 70 mg/dL and below 54 mg/dL. ADA Standards of Care 2026 recommend minimizing time below these thresholds.
Common Causes of Low Blood Sugar in Diabetes
Low blood sugar does not always mean that diabetes treatment is “too strong.” It can result from a mismatch between medication, food intake, physical activity and other factors.
- Too much insulin compared with the amount of food eaten.
- Sulfonylureas or other insulin-secretagogues that can increase insulin release.
- Skipping or delaying a meal.
- Unexpected or prolonged exercise.
- Alcohol consumption, particularly without adequate food.
- Vomiting, poor oral intake or illness.
- Changes in kidney or liver function that alter medication handling.
- Medication timing or dosing errors.
Symptoms of Low Blood Sugar
Early symptoms may include:
- Shaking or trembling
- Sweating
- Hunger
- Fast heartbeat or palpitations
- Dizziness
- Irritability or anxiety
- Headache
- Difficulty concentrating
As glucose falls further, neurological symptoms may develop, including confusion, unusual behaviour, difficulty speaking, visual problems, seizures or loss of consciousness.
What Should You Do When Blood Sugar Is Below 70 mg/dL?
If you are awake, able to swallow safely and your glucose is below 70 mg/dL, the commonly used approach is the 15-15 rule:
- Take approximately 15 grams of fast-acting carbohydrate.
- Wait about 15 minutes.
- Recheck your glucose.
- If it remains below 70 mg/dL, repeat treatment.
Examples of suitable treatments include glucose tablets or glucose gel, or an appropriate amount of regular fruit juice or non-diet soft drink. The goal is rapid absorption. High-fat foods such as chocolate are not ideal for treating an acute low because fat can slow carbohydrate absorption.
Once the glucose has recovered, consider whether you need a meal or snack, particularly if your next meal is not soon. Your individual diabetes treatment plan may require different instructions depending on your medicines, meal schedule and risk of recurrent hypoglycemia.
What If the Person Is Unconscious or Cannot Swallow?
Do not give food, drink or tablets by mouth to someone who is unconscious, having a seizure or unable to swallow safely. This creates a risk of aspiration.
Severe hypoglycemia should be treated as an emergency. Glucagon is used for severe hypoglycemia when the person cannot treat themselves. Family members and caregivers of people at high risk should know where the glucagon is kept and how to use the prescribed product. Emergency medical assistance should also be sought.
Which Diabetes Medicines Can Cause Hypoglycemia?
Insulin is a major cause of hypoglycemia, particularly when the dose is higher than needed for food intake or activity. Some medicines that stimulate insulin release, especially sulfonylureas, can also cause low blood sugar.
Many other modern diabetes medicines have a much lower risk of hypoglycemia when used alone. However, the risk can increase when they are combined with insulin or insulin-secretagogue medicines. Medication should therefore be reviewed in the context of the complete diabetes regimen rather than by looking at one medicine in isolation.
How Can Recurrent Low Blood Sugar Be Prevented?
- Review insulin doses and timing with your treating doctor.
- Do not routinely skip meals when your treatment plan depends on regular carbohydrate intake.
- Plan for exercise and monitor glucose when appropriate.
- Carry a rapid source of glucose when you are at risk of hypoglycemia.
- Review episodes occurring overnight or after exercise.
- Consider CGM when clinically appropriate, especially if lows are frequent or awareness is impaired.
- Ask whether your current diabetes medicines are contributing to recurrent hypoglycemia.
Repeated level 2 or severe hypoglycemia should prompt a review of the overall treatment plan rather than simply treating each episode separately.
Low Blood Sugar at Night
Nocturnal hypoglycemia may be harder to recognize. Some people wake with sweating, nightmares, headache or unusual fatigue, while others may not wake at all. CGM alarms can be useful for selected people at increased risk.
If nighttime lows occur repeatedly, the insulin regimen, evening food intake, exercise, alcohol exposure and other potential triggers should be reviewed with a diabetes specialist.
When Should You See an Endocrinologist?
Medical review is particularly important if you have repeated glucose readings below 70 mg/dL, any reading below 54 mg/dL, severe hypoglycemia requiring assistance, unexplained nighttime lows or symptoms of hypoglycemia without awareness.
At Vishuddha Endocrine Clinic, Ahmedabad, Dr. Moxit Shah, DM Endocrinology, evaluates diabetes treatment, insulin regimens, glucose patterns and hypoglycemia risk to individualize management.
Related Diabetes Resources
- Diabetes Management With Minimal Medicine: Lifestyle, Weight Loss & Better Blood Sugar Control
- Diabetes and Heart Protection: Why Treatment Is More Than HbA1c
- SGLT2 Inhibitors in Diabetes: Benefits, Side Effects and Sick-Day Safety
Trusted Medical Sources
- American Diabetes Association – Standards of Care in Diabetes 2026
- NIDDK – Low Blood Glucose (Hypoglycemia)
- CDC – Treatment of Low Blood Sugar
Important: This article is for general education and does not replace individualized medical advice. Do not change insulin or other diabetes medicines without discussing the change with your treating clinician.
Vishuddha Endocrine Clinic
104-105, Elite Magnum, Bhuyangdev Cross Road, Opp. Utsav Elegance, Ahmedabad, Gujarat 380061
Phone: +91 99799 92797
