Every cell in the human body needs energy to function, and one of the body’s primary sources of energy is glucose, commonly known as blood sugar.
Glucose plays an important role in supplying energy to organs and tissues, including the brain. Throughout the day, blood sugar naturally rises and falls depending on factors such as food, physical activity, hormones, and overall health.
But when blood glucose drops too low, the body can begin sending noticeable warning signals.
For many people, a blood glucose level below 70 mg/dL is considered hypoglycemia. It is particularly common among people with diabetes who take certain medications, although low blood sugar can have other causes and can occasionally affect people without diabetes.
Recognizing the possible warning signs can help you respond appropriately.
Here are 12 symptoms that may occur when blood sugar falls too low.
1. Sudden Sweating
One of the early signs of low blood sugar can be unexpected sweating.
You might suddenly feel clammy or notice that you’re sweating even though the environment isn’t particularly warm.
This happens because the body can respond to falling glucose by releasing hormones such as adrenaline. The resulting “fight-or-flight” response can trigger sweating.
Night sweats can also occur in people who experience episodes of hypoglycemia while sleeping.
However, sweating has many possible causes, so it should not automatically be attributed to blood sugar.
2. Shakiness
When glucose levels fall, the body may release adrenaline in an attempt to raise blood sugar.
This can lead to trembling or shakiness, particularly in the hands.
Some people describe the sensation as feeling weak, jittery, or unusually unsteady.
3. Sudden Hunger
An unexpected and intense feeling of hunger can also accompany low blood sugar.
The brain depends heavily on glucose for energy, so when blood sugar falls, the body may send strong signals encouraging you to eat.
If you’ve recently eaten but suddenly feel extremely hungry along with other symptoms, checking your blood glucose may be appropriate if you have access to a glucose meter.
4. Dizziness or Lightheadedness
Low blood sugar can affect how you feel physically and mentally.
Some people may become dizzy, lightheaded, or unsteady during an episode.
If dizziness is severe, persistent, or occurs with other concerning symptoms, seek medical advice rather than assuming blood sugar is the cause.
5. A Fast or Pounding Heartbeat
A noticeable increase in heart rate can occur when the body releases adrenaline in response to falling glucose.
You may suddenly become aware of your heartbeat or feel as though your heart is beating faster than usual.
This symptom can also occur for many other reasons, including anxiety, caffeine, dehydration, or certain medical conditions.
6. Irritability or Mood Changes
Blood sugar changes can affect how you feel emotionally.
During an episode of hypoglycemia, some people become unusually irritable, anxious, nervous, or emotional.
A sudden change in mood can sometimes be one of the earlier signs that blood glucose is dropping.
7. Difficulty Concentrating
The brain requires a steady supply of glucose to function normally.
When blood sugar becomes too low, you may find it harder to concentrate or think clearly.
You might struggle to complete a familiar task, lose your train of thought, or feel unusually distracted.
8. Blurred Vision
Changes in blood sugar can sometimes affect vision.
During hypoglycemia, some people experience blurred or altered vision.
Vision changes should be taken seriously, particularly if they appear suddenly or are accompanied by other neurological symptoms.
9. Headache
A headache can occur during an episode of low blood sugar.
Because headaches have numerous possible causes—including dehydration, stress, lack of sleep, and migraine—this symptom alone cannot confirm hypoglycemia.
Still, when it occurs alongside shakiness, sweating, hunger, or confusion, it may be worth checking blood glucose.
10. Weakness or Fatigue
As glucose becomes less available for energy, you may suddenly feel unusually tired or weak.
A person experiencing hypoglycemia may feel as though they have little energy even if they were feeling perfectly normal earlier.
This can happen relatively quickly, particularly when blood glucose falls significantly.
11. Confusion or Unusual Behavior
More significant hypoglycemia can affect brain function.
A person may become confused, have difficulty speaking clearly, behave differently than usual, or struggle to make decisions.
These symptoms can indicate that the situation is becoming more serious.
Someone who appears confused or unable to respond normally may need immediate assistance.
12. Seizures or Loss of Consciousness
Severe hypoglycemia can impair brain function enough to cause seizures or loss of consciousness.
This is a medical emergency.
If someone is unconscious or having a seizure, do not attempt to give them food or drink because they may not be able to swallow safely. Emergency medical assistance should be sought immediately.
What Should You Do If You Suspect Low Blood Sugar?
If you have diabetes and use a glucose meter or continuous glucose monitor, checking your blood sugar can help determine whether your symptoms are related to hypoglycemia.
For a conscious person with confirmed or suspected low blood sugar, healthcare professionals commonly recommend consuming a fast-acting source of carbohydrate and then rechecking glucose after a short period, following their individualized treatment plan.
People taking diabetes medications should discuss recurring episodes with their healthcare provider because medication adjustments may sometimes be necessary.
Low Blood Sugar Isn’t Always Caused by Diabetes
Hypoglycemia is particularly associated with diabetes treatment, but it isn’t exclusive to people with diabetes.
Other possible causes can include prolonged fasting, heavy physical activity, alcohol consumption without enough food, certain medications, and some underlying medical conditions.
If you repeatedly experience symptoms that seem consistent with low blood sugar but don’t have diabetes, it’s important to speak with a healthcare professional rather than trying to determine the cause yourself.
Listen to the Warning Signs
Low blood sugar can develop quickly, and the symptoms may initially seem easy to dismiss.
Sudden sweating, shaking, hunger, dizziness, a racing heartbeat, mood changes, or difficulty concentrating can all occur during hypoglycemia.
However, these symptoms aren’t unique to low blood sugar.
The safest approach is to consider the complete picture and, when possible, confirm glucose levels rather than relying on symptoms alone.
Most importantly, severe symptoms such as significant confusion, seizures, or loss of consciousness require urgent medical attention.