Alcohol can raise or lower blood glucose, and the lows can show up hours after the last drink, sometimes while you sleep. You do not need to be an expert to stay safer: a few simple habits go a long way. This guide is educational and does not replace advice from your doctor or diabetes care team.

Key takeaways

  • Alcohol can cause low blood glucose, including delayed lows several hours later.
  • Overnight lows are a particular concern because the liver's release of glucose is affected.
  • Avoid drinking on an empty stomach.
  • Check glucose more often than usual and keep hypo treatment close by.
  • Ask your care team what is right for your medication and situation.

Why alcohol affects blood glucose

Your liver normally helps keep glucose steady by releasing stored sugar when you need it. When alcohol is in your system, the liver gives priority to dealing with it, which can reduce that glucose release. That is why alcohol can contribute to hypoglycemia, especially when little or no food has been eaten.

The effect is not always simple. Some drinks, such as sweet cocktails or regular beer, also contain carbohydrate and can push glucose up first. The result may be a rise followed by a later drop.

Delayed and overnight lows

NHS Wales guidance notes that hypos can happen several hours after drinking, including overnight, because alcohol affects how the liver releases glucose while you sleep. This is why a normal reading at bedtime may not tell the whole story.

Low glucose can also look like being drunk: confusion, slurred speech, unsteadiness or drowsiness. Friends may miss a real low, so it helps if people you are with know you have diabetes and what to do.

Practical habits to discuss with your care team

  • Eat first and while drinking. Avoid alcohol on an empty stomach.
  • Check glucose more often. Look before you drink, during the evening and before bed. If you wear a CGM, keep alarms on. See our CGM basics guide.
  • Consider a carbohydrate snack before bed, particularly after several drinks. NHS Wales notes this can lower the risk of overnight lows.
  • Keep fast-acting carbohydrate with you, such as glucose tablets or juice, and by the bed.
  • Tell someone. A friend or family member who knows the signs of a low can step in early.
  • Plan your medication with your team. Whether and how treatment should change on a drinking day is individual, so ask before the event, not during it.

Moderation and exercise

The same guidance says alcohol limits for people with diabetes are the same as for everyone else, so check the low-risk drinking guidance for your country. Exercise also lowers glucose, so combining a night out with a hard workout the same day or next morning can add to the risk. Our guide to sick day planning is another good example of preparing ahead.

When to get help

If someone with diabetes is very drowsy, confused or cannot swallow safely, do not assume they are just drunk. Treat it as a possible low and follow your emergency plan, calling emergency services if needed. Do not leave them alone.

How DiaFitus can help

The DiaFitus app lets you log glucose readings and see how activity relates to them, which can help you notice your own patterns. It does not replace CGM alarms, medical advice or emergency care, and DiaFitus is not affiliated with any device or drink brand.

Talk to your doctor or diabetes care team about alcohol before you drink, especially if you use insulin or other medicines that can cause lows.