How to drink less: a weekly limit, standard drinks and keeping a log

How well do digital tools work?

In the 2017 Cochrane review by Kaner and colleagues (57 studies, 34,390 people), people using digital interventions drank about 23 grams less per week than controls (95% CI 15 to 30 grams, around 3 UK units). The evidence is of moderate quality.

In the 2025 trial by Garnett and colleagues (5,602 people, AUDIT 8 or above), the Drink Less app, as reported on the NHS page, led to 2.00 units more reduction per week (95% CI -3.76 to -0.24). In the pre-registered conservative analysis the difference was 0.98 units and not significant. That result belongs to Drink Less; there is no trial of Purrpose.

How many grams in a standard drink?

Kalinowski and Humphreys (2016) looked at the 37 countries with a stated definition. The most common value was 10 grams, with a range of 8 to 20. In the US a standard drink is 14 grams. In the UK a unit is 10 ml of pure alcohol, around 8 grams. We could not verify an official definition for Turkey, so "about 10 grams" is the honest wording.

How to set a weekly limit

• First write down honestly what you drank over the last two weeks. That is your starting point.
• Set the limit a little below it. Small steps are easier to keep.
• Lower it every week or two, at a pace you choose.
• Log yesterday every morning.

What logging adds

In the 2012 review by Michie and colleagues in Addiction, self-monitoring appeared alongside larger effects in brief alcohol interventions. That is an association, not proof of cause, but in practice a log shows you where you stand against your limit.

A limit is a reduction target, not permission. Alcohol is not a safe substance for health; the limit only marks the way down.