Quick answer

In the UK, start using a SAD lamp when your alarm begins going off before sunrise, which for most people falls between late September and mid October. The signal beats the date: once you are waking in the dark on most weekdays, begin daily morning sessions and keep them going until March.

Table of contents

How to tell your own autumn has started

Ask when to start using a SAD lamp in the UK and what comes back is a month. October, usually. But your October and Aberdeen's October are not the same month of light, and the better answer is a signal you can check yourself.

The alarm test

Look up sunrise for your own town, then check when your weekday alarm goes off. The morning your alarm starts beating the sun is the morning your body clock loses the bright cue it has had all summer.

For a London commuter waking at seven it lands around the start of October, since sunrise there is close to 07:00 on 1 October. In Penzance, same alarm, it has already happened: sunrise is nearer 07:20.

The fortnight test

How fast the light is going matters more than how much is left. Between 1 and 15 September, London loses roughly 54 minutes of daylight and Aberdeen roughly 68, and October repeats it.

Your own history

The best predictor of when you will want the lamp this year is when you wanted it last year. If that was the November morning you realised you had been flat for a fortnight, you started six weeks late.

Where you live changes the date

Almost nothing online mentions this. In early September, Aberdeen's sunrise is a few minutes earlier than London's, because Aberdeen sits further east: about 06:08 against 06:11 on 1 September. That advantage goes within a fortnight, and the gap then opens fast.

  • 1 October (BST): London 07:00, Aberdeen 07:10, Penzance 07:20
  • 1 November (GMT): London 06:52, Aberdeen 07:17, Penzance 07:10
  • 21 December: London 08:05, Aberdeen 08:45, Penzance 08:15

The evening goes the same way. On the shortest day Aberdeen gets under seven hours of daylight against just under eight in London.

North of roughly the Tay, bring your start date forward a fortnight against advice written for the south of England. In the far south west, mornings stay dark later into spring, so plan the wind-down later too.

Some dark mornings have nothing to do with latitude

Two people in one postcode can need different answers. Beside a south-facing window on a bright October morning you pick up useful light for free, around 1,000 lux against the 300 to 500 of a lit kitchen. Leave for a six o'clock shift and you see no daylight in December.

Feeling sluggish on dark mornings is common, and a lamp is a sensible thing to try. Low mood that persists, losing interest in what you normally enjoy, or any thought of harming yourself, is a conversation for a GP, and the NHS asks you to have it before starting anyway.

Month by month through a British winter

Times below are for London unless a place is named. Yours can be most of an hour out, so look your own town up.

September: get ready, do not start

For most of the UK there is nothing to do yet except prepare. Get the lamp out, check it works, decide where it will live. A lamp still in the cupboard in November is one you will not use.

October: the month most people should start

Sunrise on 1 October is about 07:00 in London, 07:10 in Aberdeen and 07:20 in Penzance; a fortnight later, 07:22 and 07:40. This is where the alarm test flips for most working people, and our default answer.

The clocks go back at 2am on Sunday 25 October 2026, moving London sunrise from about 07:38 on the Saturday to 06:41 on the Monday while sunset collapses from 17:50 to 16:47. That reprieve is the trap: it buys three weeks, and by mid November London is back to 07:16.

November: peak demand, and already late

November is when UK searches for SAD lamps peak, and by the light that is a month behind. Sunrise on 15 November is about 07:16 in London and 07:48 in Aberdeen, sun down before four.

December: the floor

On 21 December, London runs from roughly 08:05 to 15:55, under eight hours of daylight; Aberdeen from 08:45 to 15:30, under seven. The earliest sunset falls around 12 to 13 December, so evenings pull back while mornings keep getting later into January. A brighter tea time is not a reason to stop.

January and February: the long middle

Mornings barely improve for three weeks. London sunrise on 15 January is still about 07:57, minutes earlier than the solstice, with Aberdeen around 08:33. February is where it turns: by mid month, 07:12 and 07:35.

March: the wind-down

By 15 March, sunrise is about 06:13 in London and 06:22 in Aberdeen, and the alarm test starts failing the other way. The clocks go forward at 1am on Sunday 28 March 2027, pushing sunrise back an hour and making late March feel dark again.

Taper rather than stopping dead: shorter sessions, then alternate days, then stop once you have gone a week without missing it. The NHS puts its vitamin D window at October to early March too, and a UV-free lamp does nothing for it.

Setting up the lamp and running a morning session

First, the NHS asks you to speak to a GP. Bipolar disorder is the main one, since bright light can tip some people towards mania or hypomania, and recent mania or rapid cycling are reasons not to start unsupervised. Retinal disease and photosensitising medicines are the others: some antibiotics, lithium, St John's wort.

  1. Check the device. The NHS names three things: bright enough, with 10,000 lux the standard figure, UV-free, and a UKCA or CE mark. A daylight desk lamp is none of them.
  2. Read the small print on the lux figure. A headline lux number is quoted at a stated distance, and brands do not use the same one. Lumie's compact Mini quotes 10,000 lux at 12cm while suggesting you sit at arm's length, about 50cm. Bigger panels reach it at 35cm.
  3. Put it where you already sit, at breakfast or a desk, roughly 40 to 60cm away, the 16 to 24 inches the Mayo Clinic gives. Slightly above eye level, angled down, off to one side: in your field of vision, never stared at.
  4. Go early. Thirty minutes at 10,000 lux, within an hour of waking and generally before eight, is the protocol behind most of the research. If your lamp is dimmer, trade time for brightness: sixty minutes at 5,000 lux, or two hours at 2,500.
  5. Every day, weekends included, while doing something else. Breakfast, email, the radio. Expect one to two weeks before you can tell; some people notice in days, and some notice nothing at all.
  6. Stop three hours before bed, which is Lumie's own guidance, for the reason set out below.

Where people go wrong

Starting in December, already flat

The commonest one. You are asking the lamp to pull you back rather than hold you steady, and judging it in the worst three weeks of the year. Start anyway, and set a reminder for early October.

Using it in the evening

Bright light in the evening suppresses melatonin and delays the body clock, which is precisely backwards: later sleep onset, later waking, worse morning. If your sleep has gone sideways on evening sessions, move to mornings.

Sitting too far away

A lamp rated at 10,000 lux at 20cm, parked across a kitchen table, is not delivering 10,000 lux. Light falls off with the square of distance, so 20cm to 60cm would in principle cut it to a ninth at your eyes. Broad panels drop off more gently, but the direction is not in doubt.

Buying the wrong kind of light

A sunrise alarm ramps from dark to a modest brightness and usually peaks in the hundreds of lux: right for waking gently, nowhere near a therapy dose. A ceiling bulb is worse again, metres away and rated in lumens for the room. Our pick of the bayonet-fitting smart bulbs is the easy half of the dark-mornings problem, to buy alongside a light box.

Giving up after four days

Most guidance points at one to two weeks of consistent daily use before the effect is judgeable, and not everybody responds. Four mornings tells you nothing.

Headaches and eye strain in the first week

Common, usually mild, usually short lived, and usually from overdoing it: sessions past thirty minutes, or sitting closer than the manufacturer intends. Back the lamp off or split the session either side of breakfast. If it has not settled in a week, see a GP or optician.

Frequently asked questions

Is it too late to start a SAD lamp in December or January?

No. Late is worse than early but not the same as pointless: in January the dark season still has two good months to run. Give it a fortnight of daily use before judging it.

What time in the morning should I use a SAD lamp?

As close to waking as you can manage, ideally within the first hour and generally before eight. Morning light nudges the body clock earlier, and late sessions push it the other way.

Is a sunrise alarm clock the same as a SAD lamp?

No. Sunrise alarms wake you with a gradual ramp and typically peak in the hundreds of lux, where light boxes aim for around 10,000 lux at close range. A few claim both: read the lux figure and its stated distance.

Will a SAD lamp give me vitamin D?

No, and it is the most persistent myth about them. Lamps sold for SAD are UV-free, and vitamin D is made when UV reaches your skin, not when light reaches your eyes.

Does light therapy for seasonal affective disorder actually work?

Many people find it helps, and it is not proven to the standard a drug would have to meet. The NHS does not usually provide it because there is not enough evidence to say whether it is effective, and NICE calls the evidence uncertain. Preventive use rests on one trial of 46 people, at very low certainty.