What jet lag actually is

Jet lag is the mismatch between your internal circadian rhythm and the local time at your destination. Your body clock — anchored in the suprachiasmatic nucleus of your brain — regulates sleep, wakefulness, hormone release, body temperature, hunger and dozens of other rhythms. When you fly across time zones, this clock doesn't update instantly.

The result: feeling exhausted in the afternoon, alert at 3am, hungry at odd times, mentally foggy, and sometimes mood-disturbed. Symptoms typically last around one day per time zone crossed, untreated.

Why east is harder than west

Most people's natural circadian period is slightly longer than 24 hours, which is why staying up late feels easier than waking up early. When you fly:

• Westward (e.g. UK to USA): your day extends. Your body adapts by staying up later — which it's good at. Recovery is typically 1 day per time zone.
• Eastward (e.g. UK to Asia): your day shortens. Your body has to go to bed earlier than its natural rhythm wants. Recovery is typically 1.5–2 days per time zone.

Crossing 6+ time zones eastward is particularly tough. Most jet lag strategies focus on this scenario.

Light: the single biggest lever

Light is the dominant cue for your circadian clock. Morning light advances your clock (helpful after eastward travel); evening light delays it (helpful after westward travel).

After eastward travel (e.g. UK to Singapore, Dubai, Bangkok)

• Get morning light at destination — walk outside, sit by a window, daylight is key
• Avoid bright light in the late afternoon/evening
• Consider blue-light blocking glasses in the evening
• Aim for at least 30 minutes of outdoor light within an hour of waking

After westward travel (e.g. UK to USA, Canada)

• Stay outdoors in the late afternoon/evening at destination
• Avoid early morning bright light for the first 1–2 days
• Sunglasses help if you must be out in early morning

Sleep timing

The general principle: align with destination time as quickly as possible.

• On arrival, try to stay awake until a reasonable local bedtime (within an hour or two of normal)
• If genuinely exhausted, a short nap (under 30 minutes, before 4pm local) is fine — longer naps disrupt night sleep
• Use the morning light strategy religiously for the first 2–3 days

Pre-flight planning helps too — shifting your bedtime gradually toward destination time in the days before travel reduces the gap to bridge.

Melatonin: useful for some

Melatonin is a hormone your body naturally produces to signal sleep. Supplemental melatonin, taken at the right time, can help shift the circadian clock.

In the UK

Melatonin is prescription-only in the UK (unlike in the US, where it's an over-the-counter supplement). Independent Prescribers can supply it where appropriate — we discuss this at consultation.

How to use it (general guidance)

• Take it 30–60 minutes before your target bedtime at destination
• Dose: 0.5–3mg works for most adults. Higher doses don't necessarily help more
• Use it for 2–5 nights after arrival
• Don't use it during the day or before driving
• It's not a sleeping pill in the traditional sense — it helps shift the clock and improves sleep quality, but you may not feel immediately sleepy after taking it

Who shouldn't use it

• Pregnant or breastfeeding women
• Children (unless specifically prescribed for a medical condition)
• People with autoimmune conditions or on immunosuppressants without specialist guidance
• People with epilepsy (caution)
• People on warfarin, anti-diabetic medications, or several other interacting drugs

Meal timing

Eating aligns secondary circadian rhythms. Strategies:

• Eat at destination meal times from arrival, even if not very hungry
• Some travellers use longer fasts on the flight (12–16 hours) then breakfast at destination breakfast time — evidence is mixed but some find it helpful
• Avoid heavy meals close to local bedtime

Caffeine and alcohol

Caffeine: helpful for daytime alertness when you'd otherwise be sleepy. Avoid within 6 hours of your target bedtime.

Alcohol: generally worsens jet lag. Even though it can help you fall asleep initially, it disrupts later sleep architecture and increases nighttime waking. Skip or minimise for the first few days.

Hydration

Aircraft cabins are very dry. Mild dehydration worsens fatigue and headaches. On long flights:

• Drink 200–300ml water per hour
• Avoid excess alcohol and caffeine
• Use moisturiser and saline nasal spray if prone to dryness

The 'critical day' strategy

If you have an important meeting, performance or event soon after arrival, plan backwards:

• Arrive 1–2 days before the event if possible
• Day before event: maintain destination schedule strictly, get morning light, eat at local times
• Day of event: caffeine in the morning if needed, no naps within 4 hours of presentation, big meal afterwards rather than before

Direction-specific tips

UK to USA (westward)

Easier direction. Stay up late at destination, get evening light, aim for bedtime 1–2 hours later than natural. Often adjusts within 2–3 days.

UK to Asia (eastward)

Harder direction. Pre-trip: shift bedtime earlier by 1 hour per night for 2–3 nights before travel. On flight: try to sleep. On arrival: morning light, no afternoon naps, melatonin in early evening for 3–5 nights. Allow 4–7 days for full adjustment.

UK to Australia (very far east or west)

11–12 hours difference. Some travellers find it equally easy/hard from either direction. Multi-stage adjustment may be needed.

What doesn't work

Things that get marketed for jet lag but lack strong evidence:

• Sleeping pills as primary treatment — they help individual nights but don't shift the clock
• Most herbal 'jet lag' supplements
• 'Jet lag diets' that prescribe specific food sequences with little evidence

Book your travel consultation

Every Preston Clinic travel consultation can include jet lag planning alongside vaccines and other travel health needs. If melatonin is appropriate, we can prescribe at the same visit. Book online or walk in to Frenchwood Pharmacy on Ruskin Street.