Daytime Sleepiness

Also known asExcessive Daytime Sleepiness · Daytime Tiredness · Fatigue · Tired All the Time · Drowsiness · Afternoon Slump · 白天嗜睡 · 嗜睡 · 疲劳

What it is

Daytime sleepiness means struggling to stay awake or alert when you want to be. The most common reason is not getting enough sleep, but it can also be caused by sleep apnoea, shift work, medicines, depression, anaemia, an underactive thyroid, diabetes, vitamin B12 deficiency or alcohol.

How food and lifestyle can help

First get enough sleep and keep a regular schedule. Then, steady eating helps: a large, starchy lunch often brings on an afternoon slump, so choose balanced meals with protein, vegetables and fibre, and drink enough water, since mild dehydration makes you feel tired.

Foods and nutrients to focus on

1. Regular, balanced meals with protein and fibre instead of big starchy or sugary meals.
2. Water through the day.
3. If a blood test shows low iron or vitamin B12, iron- and B12-rich foods (red meat, fish, eggs, dairy, beans, leafy greens) or the supplement your doctor suggests.
4. Moderate caffeine early in the day: up to about 400 mg for most adults, roughly four cups of coffee.

Foods and drinks to limit

1. Sugary snacks and energy drinks for a quick lift, followed by a crash.
2. Caffeine in the afternoon, which spoils the next night's sleep.
3. Alcohol, especially in the evening.

Good to know

1. Do not drive or use machinery if you feel drowsy.
2. Tiredness that does not improve with more sleep should be checked rather than treated with supplements. See Sleep Apnea and Insomnia.
3. A 20-minute nap and a short walk in daylight can help on the day.

When to see a doctor

1. You sleep seven to nine hours but still fall asleep during the day, or you nod off in meetings, while reading or while driving.
2. You snore loudly or gasp at night, or you have headaches on waking.
3. Tiredness comes with weight changes, low mood, breathlessness, pale skin or feeling cold.

This page is general information, not medical advice. If you have a medical condition or take medicines, check changes to your diet with your doctor or a registered dietitian.

NHS — Sleep and tiredness, used for the main facts: https://www.nhs.uk/live-well/sleep-and-tiredness/