Alcohol and Blood Sugar: Risks and Safe Drinking

Alcohol and blood sugar have a complex relationship that can catch people off guard, particularly those living with diabetes. Alcohol affects the liver's ability to release glucose, which can lead to both unexpected rises and dangerous drops in blood sugar, sometimes hours after drinking. Whether you enjoy an occasional glass of wine or are managing a long-term condition, understanding how different drinks affect your glucose levels, and what precautions to take, is essential for staying safe. This article explains the key risks, which drinks have the greatest impact, and practical steps to help you drink more safely.

How does alcohol affect your blood sugar levels?

Alcohol causes the liver to prioritise metabolising alcohol over releasing glucose, which can lead to both initial blood sugar rises from sugary drinks and delayed hypoglycaemia, with the body's normal hormonal defences against low blood sugar also blunted.

Alcohol has a complex and often unpredictable effect on blood sugar levels, capable of causing both rises and falls depending on what is consumed and how much. When alcohol is absorbed into the bloodstream, the liver prioritises breaking it down over its usual role of releasing stored glucose into the blood.^[1][2] This shift in liver function is central to understanding why alcohol and blood sugar management can be difficult to balance.

In the short term, drinks that contain significant amounts of sugar, such as cocktails, liqueurs, or sweetened mixers, can cause an initial rise in blood glucose. However, as the liver continues to process alcohol, blood sugar levels may then fall, sometimes several hours after drinking has stopped. This delayed effect is particularly important for people who take insulin or certain diabetes medications.

Alcohol also impairs the body's normal hormonal responses to low blood sugar. Glucagon, a hormone that signals the liver to release glucose when levels drop, is less able to act effectively when alcohol is present, partly because the liver's capacity to produce and release glucose is already reduced by the alcohol it is processing.^[5] This means the body's usual safety mechanism against hypoglycaemia is blunted, making careful monitoring especially important. Diabetes UK and the NHS both highlight this delayed hypoglycaemia risk as a key concern for people with diabetes who drink alcohol.^[1][2]

Why can drinking alcohol cause hypoglycaemia?

Alcohol suppresses the liver's glucose release, and when combined with insulin or sulphonylureas, can cause a pronounced blood sugar drop hours after drinking, with symptoms that may be mistaken for intoxication.

Alcohol can cause hypoglycaemia (low blood sugar) primarily because it suppresses the liver's ability to produce and release glucose at a time when the body may need it most. Under normal circumstances, the liver continuously releases small amounts of glucose to maintain stable blood sugar levels between meals and overnight. When alcohol is being metabolised, this process is significantly reduced, leaving the body without its usual glucose buffer.

This risk is heightened for people with type 1 or type 2 diabetes who use insulin or sulphonylurea medications such as gliclazide or glibenclamide. These medicines already lower blood glucose, and when combined with alcohol's suppressive effect on the liver, the result can be a pronounced and potentially dangerous drop in blood sugar. Importantly, hypoglycaemia can occur many hours after drinking, including during sleep, which makes it harder to detect and treat promptly.

A further complication is that the symptoms of hypoglycaemia, including dizziness, confusion, slurred speech, and unsteadiness, closely resemble the signs of intoxication.^[6][2] This means that both the person affected and those around them may not recognise a low blood sugar episode for what it is. Anyone supporting a person with diabetes should be aware of this overlap.

If hypoglycaemia is suspected and the person is conscious and able to swallow safely, give 15 to 20 g of fast-acting carbohydrate, such as glucose tablets, a small glass of a sugary (non-diet) drink, or a small carton of fruit juice. Recheck blood glucose after 10 to 15 minutes and repeat the fast-acting carbohydrate if levels remain low. Once blood glucose has recovered, follow up with a longer-acting carbohydrate snack, such as a biscuit or a slice of bread, to help prevent a further drop. If the person is unconscious or unable to swallow safely, do not attempt to give food or drink; call 999 immediately. Wearing a medical ID bracelet and ensuring people around you know what to do in a hypo are also recommended by Diabetes UK.

Which alcoholic drinks have the biggest impact on blood glucose?

Sugary drinks such as cocktails, liqueurs, and sweet wines cause the greatest initial blood glucose spike, while spirits mixed with diet drinks have a lower immediate effect but carry a higher risk of delayed hypoglycaemia.

Sugary and carbohydrate-rich alcoholic drinks tend to cause the greatest initial spike in blood glucose, while spirits consumed without mixers have a more modest short-term effect on blood sugar but carry a higher risk of delayed hypoglycaemia. Understanding the carbohydrate content of different drinks can help people with diabetes make more informed choices.

Drinks with a higher impact on blood glucose include:

• Sweet wines and dessert wines, which contain residual sugar and can raise blood glucose quickly

• Cocktails and alcopops, which often contain fruit juice, syrups, or sugary mixers

• Liqueurs, which are typically high in sugar

• Regular lager, beer, and cider, which contain moderate to significant amounts of carbohydrate; some craft beers and ciders can be particularly high in sugars

Drinks with a lower immediate effect on blood glucose include:

• Dry wines (red, white, or rosé), which contain less residual sugar

• Spirits such as whisky, gin, or vodka, particularly when mixed with sugar-free or diet mixers

• Lower-alcohol or reduced-carbohydrate beers, though these still carry a hypoglycaemia risk

It is worth noting that even low-sugar drinks are not without risk. Spirits in particular can cause significant delayed hypoglycaemia because they suppress liver glucose output without providing carbohydrate to offset the drop. Checking blood glucose before, during, and after drinking, and not drinking on an empty stomach, are practical steps that apply regardless of the type of alcohol consumed. Diabetes UK provides guidance on the carbohydrate content of common alcoholic drinks and their likely effect on blood glucose.

Is it safe to drink alcohol if you have diabetes?

Most people with diabetes can drink alcohol in moderation following NHS guidelines of no more than 14 units per week, but those using insulin or sulphonylureas face a higher hypoglycaemia risk and should seek advice from their care team.

Many people with diabetes can drink alcohol in moderation, but doing so safely requires awareness of the risks and some practical precautions. The UK Chief Medical Officers' low-risk drinking guidelines, as published by the NHS, advise that both men and women consume no more than 14 units of alcohol per week, spread across at least three days, with several alcohol-free days each week. People with diabetes are generally advised to follow the same guidance as the wider population, as recommended by the NHS and Diabetes UK.

However, certain situations make drinking alcohol more hazardous for people with diabetes. Those who use insulin, sulphonylureas, or other glucose-lowering medicines face a higher risk of hypoglycaemia. People with poorly controlled blood sugar, diabetic neuropathy, or a history of recurrent hypoglycaemia should discuss alcohol consumption with their diabetes care team before drinking.

Alcohol can also interact with metformin. The metformin Summary of Product Characteristics advises caution with alcohol, particularly in people with renal or hepatic impairment, as excessive alcohol intake in these circumstances may increase the risk of lactic acidosis. This is not a common occurrence with moderate drinking in otherwise healthy individuals, but it is worth discussing with your prescriber if you have any concerns.

People who are pregnant or trying to conceive are advised by the NHS to avoid alcohol altogether, as no safe level of alcohol in pregnancy has been established.^[12][13]

For people managing their weight alongside blood sugar, it is also relevant that alcohol is calorie-dense and can reduce inhibitions around food choices, potentially making blood glucose management more difficult. NICE guidance on type 2 diabetes (NG28) emphasises the importance of lifestyle factors, including alcohol intake, as part of overall diabetes management.^[10][11] Anyone uncertain about whether it is safe for them personally to drink alcohol should seek advice from their GP or diabetes specialist nurse.

Tips for drinking safely when managing your blood sugar

Eating a carbohydrate-containing meal before drinking, checking blood glucose before and after, keeping fast-acting glucose to hand, and setting an overnight alarm are the most effective steps to reduce alcohol-related hypoglycaemia risk.

Several practical steps can significantly reduce the risks associated with alcohol and blood sugar for people with diabetes or those monitoring their glucose levels. Planning ahead and staying informed are the most effective tools available.

Before drinking:

• Eat a meal containing carbohydrate before or while drinking, as food slows the absorption of alcohol and greatly reduces the risk of hypoglycaemia; drinking on an empty stomach significantly increases this risk

• Check your blood glucose level and ensure it is within a safe range before you start

• Tell people you are with that you have diabetes and explain what to do if you show signs of a hypo

• Consider wearing a medical ID so that others can identify your condition in an emergency

While drinking:

• Alternate alcoholic drinks with water or sugar-free soft drinks to stay hydrated; note that water does not slow alcohol absorption, but staying hydrated is still beneficial

• Avoid very sweet cocktails or mixers with added sugar if you are trying to limit glucose spikes

• Keep fast-acting glucose (such as glucose tablets or a small carton of fruit juice) with you at all times; do not rely on diet or sugar-free drinks to treat a hypo

After drinking:

• Check your blood glucose before going to sleep and consider having a carbohydrate-containing snack if levels are on the lower side

• If you have drunk more than one or two units, consider setting an alarm to check blood glucose during the night, as hypoglycaemia risk can persist for up to 24 hours after drinking, according to Diabetes UK^[18][1]

• If you use a continuous glucose monitor or flash glucose sensor, check that any low-glucose alarms are active overnight

• Do not drive after drinking alcohol; if you have diabetes and take glucose-lowering medicines, also ensure your blood glucose is at a safe level before driving, in line with DVLA guidance on fitness to drive^[14][15]

If you experience symptoms of hypoglycaemia that do not resolve after treating with 15 to 20 g of fast-acting carbohydrate and rechecking after 10 to 15 minutes, or if someone with diabetes loses consciousness, call 999 immediately. For non-urgent concerns about managing blood sugar and alcohol, contact your GP or diabetes care team. Suspected adverse effects from any diabetes medication can be reported to the MHRA via the Yellow Card scheme at yellowcard.mhra.gov.uk.

Scientific References

1. Diabetes and alcohol.
2. Diabetes | Treatment summaries - BNF - NICE.
3. Hypoglycaemia | Treatment summaries - BNF - NICE.
4. Gliclazide: medicine for type 2 diabetes.
5. Effects of Preceding Ethanol Intake on Glucose Response to Low-Dose Glucagon in Individuals with Type 1 Diabetes.
6. Low blood sugar (hypoglycaemia).
7. Alcohol units — Calculating alcohol units.
8. Chapter 12: alcohol (Delivering Better Oral Health: an evidence-based toolkit for prevention).
9. Metformin hydrochloride Summary of Product Characteristics (representative EMC entry).
10. Type 2 diabetes in adults: management (NG28).
11. Type 2 diabetes in adults: management (NG28) — Recommendations chapter.
12. Drinking alcohol while pregnant.
13. Quality statement 1: Advice on avoiding alcohol in pregnancy (QS204).
14. Diabetes mellitus: assessing fitness to drive.
15. Diabetes and driving.
16. The Yellow Card scheme: guidance for healthcare professionals, patients and the public.
17. Adverse reactions to drugs | Medicines guidance - BNF - NICE.
18. Turner BC et al. The effect of evening alcohol consumption on next-morning glucose control in type 1 diabetes. Diabetes Care. 2001..
19. Type 1 diabetes in adults: diagnosis and management (NG17) — Recommendations.

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