---
title: "One in Five of Us Feels Unusually Tired: 8 Science-Backed Ways to Prevent Extreme Fatigue and Brain Fog"
description: Extreme tiredness and brain fog often trace back to low vitamin D, low B12, alcohol or hidden sleep apnoea. 8 proven ways to prevent them this winter.
author: Dr Marina Nani (Editor-in-Chief)
date: 2026-11-04T10:30:00.193Z
updated: 2026-11-04T10:30:00.203Z
canonical: https://richhealthmagazine.com/article/brain-fog-fatigue-prevention
image: https://cdn.nanimediahouse.com/pexels-4491432.webp
categories: Everyday Wellness
content_type: Guide
publication: Rich Health Magazine
schema_type: Article
---

If you wake up tired, lose words halfway through a sentence and read the same email three times before lunch, you are far from alone. At any given time, one in five people in the UK feels unusually tired and one in ten has fatigue that lasts, according to the Royal College of Psychiatrists.

Brain fog is not a diagnosis. It is the name for slow, cloudy thinking: trouble concentrating, finding the right word or remembering why you walked into a room. Much of it comes from causes you can measure, fix and, with the right habits, prevent.

## What Causes Extreme Fatigue and Brain Fog

The [NHS lists the usual causes](https://www.nhs.uk/live-well/sleep-and-tiredness/Why-am-i-tired-all-the-time/) of feeling tired all the time: poor sleep, stress, low iron, an underactive thyroid, sleep apnoea and diabetes. Several of these build up over months, so you adjust to feeling worse and start to call it normal. Winter adds its own pressure, with less daylight and less vitamin D.

## How to Prevent Extreme Fatigue and Brain Fog

### Take Vitamin D From October to March

Between October and early March, the sun in the UK sits too low for your skin to make enough vitamin D. The [NHS advises everyone](https://www.nhs.uk/conditions/vitamins-and-minerals/vitamin-d/) to consider a daily 10 microgram supplement through autumn and winter, and to take no more than 100 micrograms a day. If you have darker skin or spend little time outdoors, the advice is to take it all year round.

Low vitamin D is common: about one in six UK adults has low levels in their blood. In a [double-blind trial of 120 tired adults](https://pmc.ncbi.nlm.nih.gov/articles/PMC5207540) who were low in vitamin D, fatigue improved significantly more after a single high dose given by doctors than after a placebo. Seventy-two per cent of the treated group felt better, against 50% on the placebo.

### Protect Your Vitamin B12

Your body needs vitamin B12 to release energy from food and keep your nerves working. UK clinical guidance lists unexplained fatigue and 'brain fog', such as poor concentration and short-term memory lapses, among the signs of running low.

You are more at risk if you eat a plant-based diet, take metformin for diabetes or take a long-term stomach acid tablet. The UK medicines regulator warns that metformin commonly lowers B12 levels, and that the risk rises with higher doses and longer treatment. If you are vegan, the [British Dietetic Association](https://bda.uk.com/asset/5378B751-58BD-4E85-B15B360D8165A3F8) advises fortified plant milks, fortified cereals and yeast extract, or a supplement of at least 10 micrograms a day. If you take metformin, ask your GP about a B12 check.

### Keep Your Iron Topped Up

Your body needs iron to make haemoglobin, the protein in red blood cells that carries oxygen to your muscles and brain. Heavy periods, pregnancy and plant-based diets all raise your risk. Eat iron-rich foods such as beans, lentils, red meat and dark leafy greens alongside fruit or vegetables rich in vitamin C, which helps you absorb iron from plants, and keep tea and coffee away from iron-rich meals. Our guide to the [signs of iron deficiency in women](https://richhealthmagazine.com/article/iron-deficiency-symptoms-women) covers the symptoms and the blood test to ask for.

### Take Loud Snoring Seriously

About one in five UK adults may have obstructive sleep apnoea, [according to a 2026 analysis](https://www.news-medical.net/news/20260224/Untreated-sleep-apnea-may-cost-the-UK-and-US-billions-annually.aspx), and most people with it have never been diagnosed. Your throat relaxes and narrows during sleep, your breathing stops and starts, and you surface from sleep many times a night without remembering it. You can spend eight hours in bed and still wake exhausted.

The [NHS advice](https://www.nhs.uk/conditions/sleep-apnoea) to reduce the risk is to lose weight if you are overweight, sleep on your side, stop smoking and cut down on alcohol. Taping a tennis ball to the back of your pyjamas stops you rolling onto your back. If your partner hears you gasp, choke or stop breathing in your sleep, see your GP.

### Stop Drinking a Few Hours Before Bed

A nightcap helps you fall asleep faster, but the sleep it gives you breaks down later in the night. A review of 20 sleep laboratory studies found that alcohol deepened sleep in the first half of the night and increased waking in the second half, and that two or more drinks reduced REM sleep, the dreaming stage linked to memory. Alcohol also relaxes your throat muscles, which makes snoring and sleep apnoea worse. An NHS sleep service advises people with sleep apnoea to avoid alcohol for four to six hours before bed, and the same rule helps anyone who wakes at 3am.

### Move Gently, Even When You Feel Drained

Rest feels like the cure for fatigue, but gentle movement can do more. In a study of 36 inactive adults with persistent fatigue, 20 minutes of easy cycling three times a week for six weeks raised energy by 20% and cut fatigue by 65%. A harder workout cut fatigue by only 49%. An easy walk counts as low intensity: you can talk, you feel warm and you finish feeling better than when you started.

### Protect Your Brain From a Full Day of Hard Thinking

Mental exhaustion is a chemical change, not a lack of willpower. In brain scans of people doing several hours of demanding mental work, a chemical messenger called glutamate built up in the prefrontal cortex, the area that controls planning and self-control. By the end of the day, they leaned towards easy, instant-reward choices. The study was small, with 40 people, but it points to practical habits: put your hardest thinking and biggest decisions early in the day, break demanding work into blocks with real pauses, and protect your sleep, which is when your brain clears glutamate away.

### Treat Menopause Brain Fog as a Symptom

Problems with memory and concentration are among the most common symptoms of perimenopause and menopause, and they respond to treatment. NICE guidance recommends hormone replacement therapy as the first-line treatment for menopause symptoms, and cognitive behavioural therapy as an option alongside it or instead of it. A review of psychological treatments found that cognitive behavioural therapy and group programmes reduced memory and concentration difficulties. If brain fog arrives in your 40s with hot flushes, poor sleep or changing periods, talk to your GP. Our guide to [getting menopause support at work](https://richhealthmagazine.com/article/menopause-at-work-support) covers your options.

## When Tiredness Needs a GP

The NHS advises seeing a GP if you feel tired all the time and do not know why. A simple set of blood tests can check your iron stores, vitamin B12, thyroid function and blood sugar. An underactive thyroid is more common in women, and its symptoms, such as tiredness, weight gain, low mood and feeling the cold, develop so slowly that you may not notice them for years. Most of these causes can be treated once they are found.

## FAQ

**Q: What causes brain fog?**
Brain fog is a description of slow, cloudy thinking rather than a condition in its own right. Common causes include poor or broken sleep, stress, dehydration, low levels of vitamin B12, vitamin D or iron, an underactive thyroid, menopause, some medicines and recovery from infections such as COVID-19. Finding the cause usually means looking at sleep and lifestyle first, then asking a GP for blood tests if the fog persists.

**Q: What vitamin stops brain fog?**
No single vitamin stops brain fog. Low vitamin B12 and low vitamin D are both linked to fatigue and poor concentration, and low iron, a mineral, is another common cause. A supplement helps if you are low, which a blood test can confirm. In the UK, the NHS advises everyone to consider 10 micrograms of vitamin D a day from October to March.

**Q: How to clear brain fog quickly?**
For a fast lift, step away from your screen, drink a glass of water and take a brisk ten-minute walk, outdoors in daylight if you can. Switching to one task at a time also helps. If brain fog returns day after day, quick fixes will not solve it, and it is worth looking at your sleep, alcohol intake and diet, or asking a GP for blood tests.

**Q: Will brain fog ever go away?**
In most people brain fog lifts once its cause is treated, whether that means better sleep, correcting a vitamin or iron deficiency, treating an underactive thyroid or managing menopause symptoms. Improvement can take a few weeks. If your brain fog is getting worse, comes on suddenly or comes with other new symptoms, see a GP promptly.