When your blood sugar is low (hypoglycemia), your body and brain start sending warning signals, and if it keeps dropping, it can become an emergency.

What “low blood sugar” means

  • Doctors often describe hypoglycemia as blood glucose below about 70 mg/dL (around 4 mmol/L), though severe symptoms may appear below roughly 55 mg/dL.
  • It’s most common in people with diabetes (from insulin or some tablets), but it can also happen from not eating, intense exercise, alcohol, or certain illnesses.

Early warning signs

These are your body’s first “alarm bells,” mainly driven by stress hormones like adrenaline.

  • Feeling very hungry suddenly.
  • Shakiness, trembling, or feeling jittery.
  • Sweating or clammy skin, even if the room isn’t hot.
  • Fast or pounding heartbeat.
  • Feeling anxious, nervous, or irritable; some people get unusually cranky or aggressive.

Think of this phase as your body yelling: “Get sugar in, now.”

Brain (central nervous system) effects

Your brain runs almost entirely on glucose, so it reacts quickly when levels drop.

  • Lightheadedness, dizziness, or feeling like you might faint.
  • Blurry or double vision.
  • Headache and difficulty concentrating; “brain fog.”
  • Confusion, slow thinking, or trouble doing simple tasks.
  • Behavior changes: acting “off,” emotional, or unlike yourself.

If the brain keeps getting too little sugar, the situation can become dangerous.

More serious and emergency symptoms

If low blood sugar is not treated, it can progress to severe hypoglycemia, which is a medical emergency.

  • Loss of coordination; difficulty walking or using your hands properly.
  • Slurred speech that can look like alcohol or a stroke.
  • Seizures (fits).
  • Loss of consciousness, coma, and in rare cases, death.

At this stage, the person often cannot help themselves and needs someone else to give emergency treatment and call urgent medical services.

Other body effects

Low blood sugar affects many systems at once.

  • Skin: chills, pale or clammy skin, tingling or numbness around the mouth or skin.
  • Sleep: night-time lows can cause nightmares, restless sleep, or waking up sweaty and tired.
  • Heart and circulation: stress hormones raise heart rate and blood pressure temporarily.
  • Digestion: some people feel nauseous, lose appetite, or develop stomach discomfort.

What if it happens often?

Frequent lows can “train” your body to stop warning you clearly.

  • Over time, some people develop “hypoglycemia unawareness,” where the usual shaking and sweating don’t show up.
  • This makes severe episodes more likely, because you only notice when you’re already very confused or nearly passing out.

In the long run, repeated severe lows can raise the risk of heart rhythm problems and nerve damage, especially in people with diabetes.

What to do in the moment (general info)

This is general education only, not personal medical advice.

  • If you suspect low blood sugar and can safely swallow:
    1. Take a fast-acting carbohydrate (for example, glucose tablets, sugary drink, or fruit juice) in an amount recommended by your clinician (often around 15 g).
    2. Recheck how you feel and your blood sugar (if you have a meter) after about 10–15 minutes, and repeat if still low, then follow with a small snack or meal containing longer-acting carbs and some protein if advised.
  • If someone is unconscious, having a seizure, or cannot swallow safely, do not give food or drink by mouth; seek emergency medical help immediately.

When to seek urgent help

Contact a doctor or emergency services right away if:

  • Symptoms are severe (confusion, seizures, or loss of consciousness).
  • Symptoms don’t improve after treating with fast-acting sugar.
  • Lows are happening more often, or your usual warning signs seem to be disappearing.

Bottom note: Information gathered from public forums or data available on the internet and portrayed here.