Low Blood Sugar Symptoms

The sugar (glucose) levels in your blood fluctuate naturally. Low blood sugar, or hypoglycemia, can arise for many reasons, including not eating enough or suddenly engaging in strenuous activity.

However, it’s most common in those taking insulin or other medications for type 2 diabetes and those with type 1 diabetes. Hypoglycemia can be dangerous, with symptoms including rapid heartbeat, dizziness, sweating, and irritability.

This article discusses the signs of hypoglycemia, what is dangerously low blood sugar, and when it’s time to get help.

Women with diabetes laying down from a headache associated with low blood sugar

Fertnig / E+ / Getty Images

Early Signs Blood Sugar Is Low

In general, there’s a good deal of variation when it comes to the signs of low blood sugar. Milder and more common symptoms of low blood sugar include:

  • Shakiness or jitteriness
  • Hunger
  • Fatigue
  • Nausea
  • Confusion and/or irritability
  • Dizziness and/or light-headedness
  • Headache
  • Vision and/or speech difficulties
Target Blood Sugar Levels for People With Diabetes
 Before a meal  80 to 130 milligrams per deciliter (mg/dL)
 Two hours after a meal  180 mg/dL or lower
 Low blood sugar  70 mg/dL or lower
 Severe low blood sugar  54 mg/dL or lower
Blood sugar levels fluctuate naturally throughout the day but can be especially severe among those with diabetes. Here are target blood sugar levels if you have diabetes.

Nighttime Symptoms

Just as blood sugar levels can dip during the day, they can also decrease at night. Since this happens while you're asleep, it can last for many hours, leading to dangerously low levels. The signs of nocturnal hypoglycemia include:

  • Nightmares
  • Waking up and crying out
  • Excessive night sweats
  • Irritability, fatigue, and confusion upon waking up

Additional Effects of Nocturnal Hypoglycemia

Recurring low blood sugar at night can significantly impact sleep, affecting your mood, your performance at work or school, and your overall quality of life.

Serious Symptoms

Severe hypoglycemia, also known as insulin shock, occurs when blood sugar levels drop below 54 mg/dL. This is a serious condition that requires urgent medical treatment.

Extremely low blood sugar primarily impacts your brain function and can cause lasting damage. Hypoglycemic shock can cause you to pass out suddenly and, even more distressingly, cause seizures. Hypoglycemic shock can also cause:

  • Convulsions (involuntary jerky movements or shaking of the arms and legs)
  • Temporary confusion
  • Staring off into space
  • Loss of consciousness and/or spatial awareness
  • Anxiety or fear
  • Déjà vu (the mysterious feeling that you’ve already lived through what you are currently experiencing)

Signs of Hypoglycemia Unawareness

What can be especially troubling about low blood sugar is that, in some cases, there are no outward signs. This type of hypoglycemia is called hypoglycemia unawareness. There is a greater risk with this condition, as you only experience symptoms once blood sugar levels have dropped so low that they cause hypoglycemic shock.

In these cases, monitoring glucose levels regularly is essential, especially if you’re planning to drive or engage in physical activity.

Hypoglycemia unawareness is most common in those who:

  • Have had diabetes for five to 10 years
  • Frequently experience hypoglycemia
  • Take beta-blockers for high blood pressure (hypertension)   

When to Contact Your Healthcare Provider

While mild to moderate hypoglycemia can often be managed by eating snacks or drinking beverages with sugar, any sign of severe low blood sugar calls for immediate medical attention. Generally, you should contact your provider if:

  • Your blood sugar level is below 55 mg/dL.
  • You used injectable glucagon, a prescription treatment for severe hypoglycemia.
  • You experience several episodes of hypoglycemia, even if not severe, within a short span of time.

Since low blood sugar can become very severe, several cases call for emergency medical help. These include:

  • Loss of consciousness and no access to glucagon
  • Inability to restore blood sugar levels with one dose of glucagon
  • Persistent confusion despite a dose of glucagon
  • Low blood sugar levels 20 minutes after treatment


Mild to moderate hypoglycemia can generally be treated and managed without becoming serious. However, severely low blood sugar, especially if untreated, can lead to loss of consciousness or coma and become fatal. There are also complications associated with repeated hypoglycemic attacks, which can lead to hypoglycemia unawareness.

High Blood Sugar

Among those with diabetes who’ve had many hypoglycemic episodes, there is an increased chance of developing hyperglycemia (high blood sugar). This might happen if concern or fear of low blood glucose keeps you from taking medication needed to control your blood sugar.


Low blood sugar, also known as hypoglycemia, most often arises among those with diabetes and is associated with taking too much insulin. Common symptoms of mild to moderate cases include fatigue, hunger, confusion, headache, and dizziness. More severe cases can cause loss of consciousness or coma and may even become fatal. When hypoglycemia becomes severe or is resistant to treatment, prompt medical attention is necessary.

A Word From Verywell

If you have diabetes and are taking insulin, it’s important to monitor blood sugar levels and be aware of the signs of hypoglycemia. Low blood sugar can lead to serious and even dangerous health issues, but timely treatment can effectively manage it. Talk to your healthcare provider about hypoglycemia and what you can do to prevent it.

Frequently Asked Questions

  • How can you quickly raise your blood sugar?

    In mild to moderate cases of low blood sugar, consuming carbohydrate and sugar-rich foods can raise blood sugar within 15 minutes. However, medical attention is needed if the condition persists.

  • What is the diabetes 15-15 rule?

    The diabetes 15-15 rule is a way to manage mild to moderate hypoglycemia (blood sugar levels between 55 and 69 mg/dL). It involves consuming 15 grams of carbohydrates and waiting 15 minutes before checking blood sugar to see if they’re at target levels. If they aren’t, repeat the process. Once your blood sugar level is back at the target range, eat a meal or healthy snack to retain it. 

  • Can blood sugar drop while you’re sleeping?

    Yes, blood sugar levels can drop while you're sleeping. This is known as nighttime or nocturnal hypoglycemia, and can cause nightmares, yelling or shouting upon waking, and night sweats. This can be particularly problematic as blood sugar levels can remain low for multiple hours.

4 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. MedlinePlus. Low blood sugar.

  2. National Institute of Diabetes and Digestive and Kidney Diseases. Low blood glucose (hypoglycemia).

  3. Centers for Disease Control and Prevention. Low blood sugar (hypoglycemia).  

  4. Centers for Disease Control and Prevention. How to treat low blood sugar (hypoglycemia).

Additional Reading

By Mark Gurarie
Mark Gurarie is a freelance writer, editor, and adjunct lecturer of writing composition at George Washington University.