Symptoms of hypoglycemia are different for everyone and may change over time. Low glucose (blood sugar) first affects the autonomic nervous system, causing early warning signs to occur. Common mild signs and symptoms include: 

• Shakiness or tremors
• Sweating
• Hunger
• Dizziness or light-headedness
• Anxiety
• Rapid heartbeat

Other mild signs and symptoms may include:

• Chills and cold sweats
• Clamminess
• Pale skin color
• Nervousness, impatience or irritability

As hypoglycemia goes untreated, the brain begins to suffer from lower glucose. Common signs and symptoms of moderate to severe low blood glucose include:

• Headache
• Difficulty paying attention
• Confusion
• Sudden moodiness or behavior changes such as crying, sadness or anger

Other signs and symptoms of moderate to severe low blood glucose include:

• Stubbornness or combativeness
• Sleepiness or drowsiness
• Nausea
• Cloudy or blurred vision
• Tingling sensation or numbness in the lips or tongue
• Clumsy or jerky movements
• Lack of coordination
• Convulsions
• Fainting/loss of consciousness

People with diabetes should also be aware of the symptoms of nighttime hypoglycemia – low blood glucose in the middle of the night. These may include:

• Sheets and pajamas damp from sweat.
• Nightmares or restless sleep.
• Waking up with a headache.
• Rapid heartbeat.
• Still feeling tired in the morning.
• Unusually high glucose readings in the morning (rebound hyperglycemia, also known as the Somogyi effect). The body can try to counteract the low glucose by releasing hormones that raise blood glucose.

Some people do not feel or recognize the symptoms of low blood glucose. This problem is known as hypoglycemia unawareness. Patients may have hypoglycemia unawareness if their blood glucose level drops below 50 milligrams per deciliter (mg/dL) without any symptoms.

The more episodes of hypoglycemia that occur, the harder it is for the body to detect the next episode. The body becomes less sensitive to the symptoms over time, making it a dangerous condition. The emotional and physical symptoms (e.g., shakiness, dizziness, hunger) may begin to fade after five years with diabetes. After 20 or more years, it is not uncommon for these symptoms to become too subtle to feel or recognize.

However, the mental symptoms of low glucose (e.g., difficulty paying attention, lack of coordination) do not fade. Over time, these subtle symptoms may become a patient’s best signal of low glucose.

It is important for people with diabetes to check their glucose levels often and to treat low glucose even when they feel fine, as recommended by their physician. Left undetected and untreated, low glucose can lead to permanent brain damage or a potentially fatal diabetic coma.