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A good measure: Units and drinking guidelines

What is a unit of alcohol?

In the UK, consumption of alcoholic drinks is measured in units. Units are a simple way of expressing the quantity of pure alcohol in a drink, offering a standardised comparison of the volume of pure alcohol between alcoholic beverages.[1] They are calculated as follows:


In the UK, 1 unit is equal to 8 grammes of pure alcohol, which is also equivalent to 10 millilitres of pure ethanol (alcohol). This takes approximately an hour for the average adult to process in the body (although there are many varying factors which mean all drinkers process alcohol differently).[2] The number of grammes that make up a unit varies between countries.**

UK low risk drinking guidelines

The current advice from the Department of Health regarding alcohol consumption falls into 3 categories: 1) regular drinking; 2) single episode drinking; 3) pregnancy and drinking. Advice is as follows:[3]

Figure 2a: On regular drinking


Figure 2b: On single episode drinking episodes


Figure 2c: On pregnancy and drinking


Hazardous drinking is defined as a pattern of drinking which brings about the risk of physical or psychological harm. This occurs when a person regularly drinks over the recommended daily limit. The cumulative effect over a week's worth of drinking will most likely exceed 21 units for men and 14 units for women.

Harmful drinking, a subset of hazardous drinking, is defined as a pattern of drinking which is likely to cause physical or psychological harm.[4] Men who drink more than 50 units in the course of a week are classified as harmful drinkers, as are women who consume over 35 units. Figure 2 depicts the difference in consumption levels between moderate, hazardous and harmful drinkers.

History of UK drinking guidelines

The current recommended drinking guidelines were originally based on evidence submitted in a report by the Royal College of Physicians (RCP) to the UK government in 1987. This report acknowledged that there was “insufficient evidence to make completely confident statements about how much alcohol is safe”.[5] However, in making the judgement that the public needed to be informed about the risks associated with drinking, it suggested the following guidelines for 'sensible limits of drinking':

  • Men – no more than 21 units per week
  • Women – no more than 14 units per week
  • Both men and women should have 2 or 3 alcohol-free days
  • The total number of weekly units should not be drunk in 1 or 2 bouts 

These guidelines were based on the underlying assumption that they did not apply to children and adolescents, to adults who had particular health problems or a family history of alcohol problems or to women during pregnancy.

In 1995, the recommendations were reviewed by an inter-departmental government working group, following the publication of scientific evidence stating that small amounts of alcohol may have a protective effect against coronary heart disease. Despite this finding, leading health experts – including the British Medical Association (BMA)[6] and the RCP – came to the conclusion that the 1987 guidelines were still the most appropriate means of communicating to the public the risks associated with drinking.[7]

However, it was agreed that further clauses could be added to take account of short term episodes of heavy drinking which was argued to often correlate strongly with both medical and social harm. The Sensible Drinking report called for the establishment of daily benchmarks to help individuals 'decide how much to drink on single occasions and to avoid excessive drinking with its attendant health and social risks'.[8]

These new guidelines recommended that 'men should not regularly drink more than 3–4 units of alcohol a day and women should not regularly drink more than 2–3 units a day', and advised against the consumption of alcohol for at least 48 hours after an episode of heavy drinking, in order to allow affected parts of the body to recover fully.

The transition from weekly to daily guidelines effectively increased the weekly limit for men by 33% and women 50%, exceeding the previous threshold for low risk drinking as presented by the medical profession. These changes were met with concern by the health community, as they contradicted the evidence base and seemingly recommended 'safe' levels of drinking that were in fact over and above what was deemed a 'low risk' threshold.

The 1995 report also extended the reach of the original recommendations to include guidance for pregnant women. They were warned against drinking alcohol – especially in the first three months of the pregnancy to lower the risk of miscarriage – but that if they did still drink, to consume not more than 1–2 units of alcohol once or twice a week and not to become intoxicated.

In 2009 the outgoing Chief Medical Officer (CMO) for England, Sir Liam Donaldson, introduced a new guideline, that no children under the age of 15 years should consume alcohol, after evidence indicated that drinking before this age increased the risk of alcohol dependency in later life and also affected cognitive development. The CMO guidance recommended:

An alcohol-free childhood is the healthiest and best option, but;[9]

  • If children do drink alcohol, they should not do so until at least 15 years old;
  • If 15 to 17 year-olds drink alcohol, it should be rarely, and never more than once a week. They should always be supervised by a parent or carer; and
  • If 15 to 17 year-olds drink alcohol, they should never exceed the recommended adult daily limits (3–4 units of alcohol for men and 2–3 units for women)

In December 2011, the House of Commons Science and Technology Committee launched an inquiry into the current UK drinking guidelines, calling for a review of the evidence that had emerged since 1995 on the health risks associated with drinking, and also on levels of public understanding of the guidelines. The Committee received evidence from a number of organisations, including public health interest groups and the alcohol industry.

The Science and Technology Committee report, published in January 2012, concluded:

There are sufficient concerns about the current drinking guidelines to suggest that a thorough review of the evidence concerning alcohol and health risks is due. The Department of Health and devolved health departments should establish a working group to review the evidence and advise whether the guidelines should be changed. In the meantime, the evidence suggests that (i) in the context of the current daily guidelines, the public should be advised to take at least two alcohol-free days a week; and (ii) the sensible drinking limits should not be increased.[10]


The Coalition Government's Alcohol Strategy, published in March 2012, accepted a need to improve the UK public's poor understanding of and adherence to the current drinking guidelines, with around a third of adult men and a fifth of adult women drinking above the recommended limits. In order to tackle this problem, the Government tasked the current CMOs (including the newly appointed chief for England, Dame Sally Davies) with overseeing a review of the drinking guidelines, which would:

take account of available science on how we can best communicate the risks from alcohol, improving the public's understanding of both personal risks and societal harms. This will include whether separate advice is desirable for the maximum amount of alcohol to be drunk in one occasion and for people over 65. This could complement the existing guidelines for young people and women who are pregnant or trying to conceive.[11]

After 21/2 years of discussions with 3 independent groups of experts, the UK Chief Medical Officers published the latest set of guidelines in January 2016, setting out 3 main recommendations on: 1) regular drinking; 2) single episode drinking; and 3) advice on drinking in pregnancy (as aforementioned).

A weekly, rather than a daily, guideline was recommended by the experts, the reasoning being that a weekly format "should be an easier benchmark for people (most of the population) who do not drink alcohol daily".

The latest evidence also suggests that the group benefits for heart health of drinking alcohol are less and apply to a smaller group of the population than previously thought. The only group with potential to have a overall significant reduction in risk of death in the UK is women over the age of 55 (especially if drinking around 5 units a week or less); there are adverse effects from drinking alcohol on a range of cancers – this was not fully understood in 1995 – and these risks start from any level of regular drinking and then rise with the amounts of alcohol being drunk.

The summary goes on to state that:

if people did drink at or above the low risk level advised, overall any protective effect from alcohol on deaths is overridden, and the risk of dying from an alcohol-related condition would be expected to be around, or a little under, 1% over a lifetime. This level of risk is comparable to risks from some other regular or routine activities, such as driving.


The expert group was also quite clear that there are a number of serious diseases, including certain cancers, that can be caused even when drinking less than 14 units weekly; and whilst they judge the risks to be low, this means there is no level of regular drinking that can be considered as completely safe. These are risks that people can reduce further, by choosing to drink less than the weekly guideline, or not to drink at all, if they wish. There is also evidence that adopting alcohol free days is a way that drinkers who wish to moderate their consumption can  find useful.  

**   A comprehensive international roundup of drinking guidelines by nation is available on Wikipedia.


[1]   BBC News Health (November 2011), 'Health Explained: What is a unit of alcohol?'

[2]   NHS Choices, 'Alcohol Units'

[4]   Health & Social Care Information Centre (HSCIC) (May 2012), 'Statistics on Alcohol: England, 2012', p. 9

[5]   Royal College of Physicians (1987), 'The medical consequences of alcohol abuse, a great and growing evil', Tavistock Publications Ltd

[6]   British Medical Association (BMA) (1995), 'Alcohol: guidelines on sensible drinking', BMA, London

[7]   Royal College of Physicians, Royal College of Psychiatrists, Royal College of General Practitioners (1995), 'Alcohol and the Heart in Perspective, sensible limits reaffirmed', Oxprint, Oxford

[8]   Department of Health (December 1995), 'Sensible Drinking – The report of an Inter-Departmental Working Group', DH, London, p. 24

[9]   Donaldson, Liam, (Sir) (December 2009), 'Guidance on the consumption of alcohol by children and young people. A report by the Chief Medical Officer', Department of Health, pp. 13–29

[10]   House of Commons Science and Technology Committee (December 2011), 'Alcohol guidelines: eleventh report of session 2010-12', p. 3

[11]   Secretary of State for the Home Department (March 2012), 'The Government's Alcohol Strategy', p. 24