Hypoglycaemia is generally defined as blood glucose below 70 mg/dL (3.9 mmol/L). Below 54 mg/dL (3.0 mmol/L) is clinically significant and needs immediate treatment regardless of how you feel.
How it feels
Early symptoms come from adrenaline as the body tries to raise glucose itself: shakiness, sweating, a pounding heart, anxiety, sudden hunger, pallor, tingling around the lips. If glucose keeps falling, the brain itself runs short of fuel: difficulty concentrating, slurred speech, blurred vision, uncharacteristic irritability or confusion, clumsiness, drowsiness. At the extreme, seizure or loss of consciousness.
Symptoms differ between people and can change over the years. Some people first notice it as a mood shift that those around them spot before they do.
The 15-15 rule
- Take 15 grams of fast-acting carbohydrate. Half a cup (120 ml) of fruit juice or regular soft drink; three or four glucose tablets; a tablespoon of sugar, honey or jam; three or four dates.
- Wait 15 minutes. This is the hard part. Do not keep eating because you do not feel better yet — the glucose has not reached your bloodstream. Over-treating is what turns a low into a high two hours later.
- Re-check. Still below 70? Repeat the 15 grams.
- Once you are back above 70 and your next meal is more than an hour away, eat something with protein and slower carbohydrate — bread and cheese, biscuits and milk — to stop it falling again.
Chocolate, ice cream and most pastries are poor choices for treating a low. Fat slows absorption, which is exactly the wrong property here.
Severe hypoglycaemia
If someone is unconscious, having a seizure, or is too confused to swallow safely:
- Do not put food or drink in their mouth. They may aspirate it.
- Turn them on their side.
- Give glucagon if it is available and you have been shown how — injection or nasal powder.
- Call emergency services.
Anyone using insulin or sulfonylureas should have a glucagon kit at home, and at least one person they live or work with should know where it is and how to use it. That conversation takes five minutes and is worth having today rather than during the event.
Hypoglycaemia unawareness
After repeated lows, the adrenaline warning system can stop firing. People lose their early symptoms and go straight from feeling normal to being confused. This is dangerous and it is also reversible: strictly avoiding all lows for two to three weeks — usually by loosening targets temporarily with your doctor's guidance — often restores the warning signs. If you no longer feel your lows, tell your care team. It changes how they will treat you, and it may affect driving advice where you live.
Common causes worth checking
- Too much insulin, or the wrong insulin taken by mistake
- A meal delayed or skipped after taking a dose
- Eating fewer carbohydrates than the dose was calculated for
- Unplanned or unusually long exercise — the effect can appear hours later, including overnight
- Alcohol, which blocks the liver from releasing stored glucose. An alcohol-related low can arrive many hours afterwards, typically during sleep.
- Improving kidney function or weight loss changing how long insulin lasts
Log every low, even the mild ones you handled easily. Three mild lows in a week at roughly the same time of day is a dosing pattern, and it is the kind of thing that is invisible in memory but obvious in a log.