Insulin and alcohol: low blood sugar risks and how to reduce them

Insulin lowers blood sugar. That is its job, and it is the reason people with type 1 diabetes and many with type 2 diabetes depend on it. The NHS explains that diabetes medicines treat the condition by lowering blood sugar, but can sometimes make it go too low, and that this is common with insulin.

Alcohol enters the picture because the NHS lists it as one of the things that make a hypo more likely. On its low blood sugar page, drinking a lot of alcohol, particularly without eating, appears alongside taking too much insulin, injecting problems, missed or delayed meals, not eating enough carbohydrate and exercising without adjusting food or insulin. The long-acting insulin page makes the same point: a person might have a hypo if they drink alcohol, especially after skipping a meal.

The NHS pages do not set out the physiology and this guide will not guess at it. The practical message is enough: alcohol is on the list of triggers and the usual safeguards are eating, drinking moderately and planning ahead.

The NHS low blood sugar page gives short, direct advice for people who take diabetes medicines. Under what to do, it lists following the treatment plan agreed with your diabetes care team, including adjusting insulin when needed, checking blood sugar regularly, carrying something to raise it quickly, carrying a glucagon kit and medical ID, and making sure family and friends know how to treat a severe hypo. Under what not to do, it says not to skip or delay meals, not to drink too much alcohol and not to drink alcohol without eating.

The alcohol advice is specific: keep to the recommended guidelines of no more than 14 units a week, spread over 3 days or more. That is the general UK guideline, so it applies to everyone, but the NHS places it in the low blood sugar section because it matters more when insulin is involved.

If you have type 1 diabetes and often have problems with low blood sugar, the NHS suggests asking your diabetes care team about switching to an insulin pump and about a continuous or flash glucose monitor. Those are questions to raise before, not after, a bad night.

The NHS lists the symptoms of low blood sugar as feeling hungry, dizzy, anxious or irritable, sweating, shaking, tingling lips, heart palpitations, tiredness or weakness, blurred vision and confusion. In severe cases a person may have a seizure or become unconscious.

Treatment follows the steps the NHS describes: eat or drink something that raises blood sugar quickly, such as a small glass of fruit juice or a sugary fizzy drink, 5 glucose or dextrose tablets, 4 large jelly babies or 2 tubes of glucose gel; check your blood sugar after 10 to 15 minutes; repeat if it is still below 4mmol/L; and once above 4mmol/L, eat something that lasts longer, such as biscuits, a sandwich or your next meal.

Because several hypo symptoms, such as confusion, difficulty concentrating and dizziness, can also appear when someone has been drinking, they can be put down to the alcohol. The NHS treats having been drinking as a reason for extra caution. If you are with someone who has diabetes and has been drinking, do not assume they are simply drunk.

The NHS says that if you think someone has very low blood sugar and they are not responding normally or are unconscious, you should not give food or drink because they cannot swallow safely. Put them in the recovery position and give a glucagon injection straight away if one is available and you know how to use it.

Call 999 if a glucagon injection is not available or you do not know how to use it, if you have given one and they have not recovered within 10 minutes, or if they have been drinking alcohol. The insulin pages repeat the same triggers for a severe hypo. This is why the alcohol question matters beyond the drinker: friends and family need to know that a person with diabetes who has been drinking and cannot be woken needs an ambulance.

See a GP, or speak to your diabetes care team, if you often get hypos, have had severe hypos or hypos at night, or do not always recognise the symptoms.

The long-acting insulin page says blood sugar can go too low while you are asleep, and that you may wake at night feeling sweaty and confused or feel tired or have a headache in the morning. It advises speaking to your diabetes team if you think you are having hypos at night. A night out is exactly the situation in which this can happen, so planning a snack and a blood sugar check before bed is worth discussing with your team.

The NHS says that if you drive you need to check your blood sugar before each journey and then every 2 hours while driving, and not to drive for at least 45 minutes after blood sugar is back to normal following a hypo. The DVLA has further information on diabetes and driving.

Your diabetes team can talk through alcohol in an ordinary, practical way. Private clinics and pharmacists can help too, but they will not see your readings unless you bring them.