How to Not Be Hungover: NHS Advice and What the Trials Found

The only way to avoid a hangover is to drink less alcohol, or none. The UK's systematic review of hangover trials puts it as "abstinence or moderation", and the NHS advises no more than 14 units a week, spread over three or more days. Across 21 placebo-controlled trials of hangover products, no intervention was tested twice and every efficacy result was rated very low quality.^1,2,3 This page is the Wellgard hangover guide: the NHS advice in its own words, what the trials found, what does change the next day, and the page that answers each question.

What does the NHS advise about drinking?

In the NHS's words: "men and women are advised not to drink more than 14 units a week on a regular basis"; "spread your drinking over 3 or more days if you regularly drink as much as 14 units a week"; "try to have several drink-free days each week". And the sentence that frames the subject: "If you drink less than 14 units a week, this is considered low-risk drinking. It's called 'low risk' rather than 'safe' because there's no safe drinking level." Binge drinking means "drinking more than 8 units of alcohol in a single session for men, or more than 6 units in a single session for women". For a single occasion the NHS lists four things: "limit how much you drink; drink more slowly; drink with food; alternate your drinks with water or non-alcoholic drinks".²

The unit behind it: "One unit equals 10ml or 8g of pure alcohol, which is around the amount of alcohol the average adult can process in an hour", so "within an hour there should be, in theory, little or no alcohol left in the blood of an adult, although this will vary from person to person".⁴ A pint, a large wine or a double is more than one; how many units are in a drink does the arithmetic.

What have the trials of hangover products found?

The 2022 systematic review from King's College London is the fullest answer. It found 21 placebo-controlled randomised trials, 386 participants in all, and "No two studies reported on the same intervention; as such, meta-analysis could not be undertaken." Every efficacy outcome was rated very low quality because of "methodological concerns and imprecision". Seven interventions showed a statistically significant difference in one small trial each: five food-derived ingredients (clove extract, a Hovenia dulcis fruit extract, L-cysteine, red ginseng and Korean pear juice) and two medicines. None was tested a second time. The conclusion: "Only very low quality evidence of efficacy is available to recommend any pharmacologically active intervention".³ The 2005 BMJ review of eight earlier trials reached the same place: "The most effective way to avoid the symptoms of alcohol induced hangover is to practise abstinence or moderation."¹

The MHRA, the medicines regulator, regards a product offered for hangovers or their symptoms as a medicine that needs a licence, so no supplement, drink or patch sold in the UK may lawfully make a hangover claim, and this page makes none.⁵ Trial by trial, with sizes, designs, funding and quality ratings, the evidence is set out in what the trials of hangover pills and supplements found.

What actually changes how you feel the next day?

Six things have been measured against next-day outcomes. These are associations and blood-alcohol measurements, not a plan for a night out.²

The hours before a drink, folklore included, are on what to eat and drink before drinking alcohol.

What is a hangover and why does it happen?

The research field's 2020 definition: "The alcohol hangover refers to the combination of negative mental and physical symptoms which can be experienced after a single episode of alcohol consumption, starting when blood alcohol concentration (BAC) approaches zero." Hangovers are "more likely when subjects consume more alcohol than they usually do" and "can start at any time of day or night, whenever BAC approaches zero".¹⁵ In a survey of 1,410 students, fatigue (95.5%) and thirst (89.1%) were the commonest symptoms, but analysed together drowsiness explained 28.8% of the variation and the thirst-and-dry-mouth factor under 5%: "Drowsiness and impaired cognitive functioning are the two dominant features of alcohol hangover."¹⁶ The biology is on what causes a hangover.

How long does a hangover last, and when is it worst?

Usually a day, and lighter as it goes. When 727 drinkers' latest hangovers were charted, 54.5% declined continuously from the morning, 19.1% stayed flat all day and 21.8% rose then fell, with more stomach symptoms.¹⁷ Hourly, hangover-sensitive drinkers scored 6.1 out of 10 at 09:30 and 3.3 at 15:30, and symptoms were "still present in the afternoon".^18,19 Drinkaware, the UK alcohol charity, says symptoms "tend to peak around the time your body has reduced the amount of alcohol in your system to zero, and can last for up to 24 hours afterwards".²⁰ No peer-reviewed study of a hangover lasting into a second day was found; Drinkaware reads longer-lasting symptoms as possible "drinking at a high-risk level"²⁰ (the NHS wording is in the final section), and "still hungover two days later" is answered on why your hangovers feel so bad.

Should you be sick when hungover?

Vomiting is a symptom, not a method: the hangover pattern that rose then fell through the day was "characterized by the increased presence of gastrointestinal complaints", and nausea passes with it.¹⁷ No study has tested making yourself sick, and the NHS, writing about someone who has drunk far too much, says "do not try to make them sick".²¹ If you cannot keep fluids down, the NHS dehydration page says: "Ask for an urgent GP appointment or get help from NHS 111 if: you're feeling unusually tired; you feel dizzy when you stand up and it does not go away; you have dark yellow pee or you're peeing less than normal".²²

What should you not do when hungover?

Drink more alcohol. "There's no safe drinking level", and hair of the dog is next.² Assume the alcohol has gone. At about a unit an hour, a heavy night can still be in the blood at breakfast, "although this will vary from person to person".⁴ Take a painkiller without reading the NHS page for it. The paracetamol page says it may not be suitable if "you're dependent on alcohol or binge drink"; speak to a pharmacist.²³ Count on going back to bed. Short sleep is associated with worse hangovers, but no trial has measured whether extra sleep in the morning changes the day's course.⁸

What about hair of the dog?

No trial has tested it. By the field's definition a hangover begins "when blood alcohol concentration (BAC) approaches zero", so another drink does not change the hangover, it postpones the moment it starts.¹⁵ Set beside "there's no safe drinking level", it is the one thing on this page the evidence rules out.²

Does what you eat or drink the next morning make a difference?

The NHS hydration guidance is general: "the government recommends that people should aim to drink 6 to 8 cups or glasses of fluid a day", and "water is the best way to replace lost fluids".²⁴ That answers thirst; it is not a lever on the hangover, because the amount of water drunk once hungover "was not related to changes of hangover severity and thirst".¹³ In the oldest trial, 109 men given alcohol after a fast, fructose or glucose corrected the low blood sugar of the hangover period but had no significant effect on "the intensity of alcohol intoxication and hangover".²⁵ What electrolytes are explains what a sachet contains, without reference to drinking. Food by food, the answer is what to eat and drink with a hangover.

Why do some people feel anxious the day after?

Because the hangover reaches mood. A 2026 pre-registered systematic review of 22 studies in 6,152 people found "a significant association between hangovers and increased negative affect, including anxiety, stress and depression", worse where "repetitive negative thinking and greater baseline anxiety" were present.²⁶ The NHS puts it plainly: "hangovers often make you feel anxious and low."¹⁰ Hangover anxiety covers who is most affected and the NHS routes if the anxiety is there on days you have not been drinking.

Why does alcohol wake you up at 3am?

Because it changes the shape of the night. The review of the laboratory studies in healthy volunteers: "At all dosages, alcohol causes a reduction in sleep onset latency, a more consolidated first half sleep and an increase in sleep disruption in the second half of sleep"; the first REM period is delayed at every dose.²⁷ The nightcap that sends you off quickly is what has you awake at 3am. The mechanism is on why alcohol wakes you up at 3am; bedtime drinks are graded on what to drink before bed for sleep, under "Does a nightcap help you sleep?".

Frequently asked questions

How long does alcohol stay in your system?

The NHS: one unit is "around the amount of alcohol the average adult can process in an hour", and this "will vary from person to person".⁴ Six units is, in theory, six hours, moved by size, sex and food. The detail is on how long alcohol stays in your system.

What is the 20 minute rule for alcohol?

In UK coverage it is a pacing habit: when you want a drink, wait 20 minutes before having it, at the start of the evening and between drinks, so that each one is a decision rather than a reflex; the rationale given is that an urge usually passes within minutes. No trial has tested it. The physiology does say a drink is not fully in your blood when the glass is empty: in 16 people, breath alcohol peaked on average 22 minutes after drinking with a meal, and fasting drinkers overshot within about 40 minutes.¹¹ The NHS version is shorter: "drink more slowly" and "alternate your drinks with water or non-alcoholic drinks".²

Do hangovers get worse as you get older?

The evidence runs the other way. In 51,645 Danish adults aged 18 to 94, the odds of a severe hangover after a binge were 6.8, 4.8, 3.0 and 2.0 for men aged 18 to 29, 30 to 39, 40 to 49 and 50 to 59 compared with men over 60, with similar results for women, and the difference was not explained by usual intake, binge frequency or eating with alcohol.²⁸

Is a hangover just dehydration?

No. In the blood studies, "markers of dehydration (e.g., vasopressin) were not significantly related to hangover severity", and nor were electrolytes, glucose, lactate or cortisol.²⁹ The 2024 review concludes that "alcohol hangover and dehydration are two co-occurring but independent consequences of alcohol consumption": thirst passes in hours, the hangover does not.¹³

What are the signs it is more than a hangover?

The NHS alcohol poisoning page: "Call 999 if: you think someone has alcohol poisoning; you or someone else has had a seizure or fit; someone has lost consciousness; someone has stopped breathing." While you wait, "stay with them" and "sit them up if they're awake, or put them in the recovery position if they've passed out".²¹ A hangover still severe on the second day, or after every ordinary evening, belongs with the when-to-worry section of "why your hangovers feel so bad" and, if it is a pattern, with a GP.

If you are worried about your drinking

"Drinkline is the national alcohol helpline. If you're worried about your own or someone else's drinking, you can call this free helpline in complete confidence. Call 0300 123 1110 (weekdays 9am to 8pm, weekends 11am to 4pm)." "A good place to start is with a GP."³⁰ In Scotland, NHS inform lists Drinkline Scotland on 0800 7314 314.³¹ "Call 999 if: you think someone has alcohol poisoning; you or someone else has had a seizure or fit; someone has lost consciousness; someone has stopped breathing."²¹ Because this page covers symptoms lasting beyond a day: "If you stop drinking or cut down, you may get withdrawal symptoms. This is a sign your body is dependent on alcohol." and "It can be very dangerous to stop drinking suddenly if you're dependent on alcohol. If you get withdrawal symptoms, get medical help before you try to stop drinking."³²

Sources

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