Brain Fog: Everyday Causes and Habits That Help You Think Clearly

Reviewed by Dr. Tracy Gibbs, PhD, Head of R&D · Last updated: 2026-10

Brain fog is the feeling that your thinking has slowed down: you lose your train of thought, reread the same email and struggle to find the right word. On an ordinary week, the most common causes are short sleep, not drinking enough, stress, constant task switching and a long day without moving. Most of these respond to simple changes, and if the fog arrives suddenly, lasts for weeks or comes with other symptoms, it is a reason to see a doctor.

What does brain fog feel like?

It is 10:40 on a Tuesday. You open a document to finish one paragraph, check a message that just came in, go back to the document and realize you have no idea what the paragraph was meant to say. You walk into the kitchen and forget why. Someone asks a simple question in a meeting and the answer takes a beat too long.

Brain fog is a description, not a diagnosis: slow thinking, poor focus, forgetfulness. This article is about the everyday version that follows a short night or a chaotic week. The last section covers when it may point to something else.

What causes brain fog?

Is your sleep behind the fog?

Sleep is the first thing to check. The US National Heart, Lung, and Blood Institute lists the effects of sleep deficiency plainly: trouble making decisions, solving problems and remembering things, slower reactions and more mistakes [1].

What makes short sleep tricky is that you get used to it. In a laboratory study at the University of Pennsylvania, 48 healthy adults were limited to 4, 6 or 8 hours in bed for 14 days in a row. On 6 hours a night, performance on every cognitive test declined steadily, until it matched the level seen after up to two nights without any sleep at all. Yet their own sleepiness ratings rose at first and then barely changed, while performance kept slipping [2].

That is the classic fog after a week of late nights: you think you have adapted, and you have not. The American Academy of Sleep Medicine and the Sleep Research Society recommend seven or more hours a night for healthy adults [3]. If you struggle to fall asleep because your mind will not switch off, read can't fall asleep. If you fall asleep easily but wake too early, read why you wake up at 4am.

Can dehydration cause brain fog?

It can contribute. A meta-analysis of 33 studies found that dehydration impairs attention, executive function and motor coordination, with the clearest effects once water loss exceeds 2% of body mass [4]. For a person weighing 70 kg, that is about 1.4 kg of water.

Keep a bottle within reach and drink with every meal. If your fog tends to arrive in the middle of the afternoon, our article on the 3 PM slump looks at the role of water, light and lunch at that hour.

How does stress cloud your thinking?

The prefrontal cortex, the area behind your forehead, holds information in mind, plans the next step and keeps you on task. Yale neuroscientist Amy Arnsten has shown that even mild stress that feels out of your control can cause a rapid loss of prefrontal function, while older, more reflexive brain circuits take over [5]. That shift is useful when you need to react fast. It is unhelpful when you need to write a proposal.

So the deadline that makes you anxious can also make you worse at meeting it. Write down one next action, step away for a few minutes and deal with one problem at a time. For more, read how to stay calm on a stressful day.

Does multitasking cause brain fog?

It makes the feeling worse. In a series of four experiments, people who alternated between two tasks were consistently slower than people who repeated one task, and the cost of each switch grew as the rules of the tasks became more complex [6]. A workday of email, chat, calls and a report in between is a long chain of those switches.

Your phone adds to it even when you ignore it. In one study, simply receiving a call or text notification during an attention task disrupted performance about as much as answering or replying [7]. Try one block of about an hour a day with notifications off and the phone in a drawer, and give it the task that needs your best thinking.

What about food and blood sugar?

Meals matter, though the research is more modest than many headlines suggest. A review of studies in healthy adults found a small but consistent memory advantage after eating breakfast, mostly for recalling information later in the day. The evidence on which breakfast works best is still limited [8].

In practice, do not run a demanding morning on coffee alone. The early afternoon dip, and what lunch has to do with it, is covered in the 3 PM slump.

Can a walk clear your head?

A short one can help. A meta-analysis of 79 studies found that a single bout of exercise has a small positive effect on cognitive performance, seen during the exercise, right after it and after a delay [9]. The effect is small, and it costs nothing. A ten-minute walk between two meetings, ideally outside, is the easiest version.

How to get rid of brain fog: a daily routine

• Protect seven hours. Seven or more hours, with the same wake-up time every day [3].
• Keep water close. A glass in the morning and one with every meal.
• Eat breakfast on demanding days. Keep lunch moderate.
• Work in single-task blocks. One task, notifications off, phone out of sight [6][7].
• Move every few hours. A ten-minute walk is an easy start.
• Write down the next step. When stress builds, put one concrete action on paper.

Where Smart Strips fit

Habits do the heavy lifting. For the days when you need a clear head for a specific task, Smart Strips Focus is made for that moment. Each oral dissolvable strip contains 20 mg Alpha-GPC, 20 mg caffeine, 10 mg L-theanine, 10 mg citicoline and 5 mg phosphatidylserine, with a mint flavor. You place it on your tongue, press it gently against the roof of your mouth and it dissolves in 7 to 30 seconds, with no water. Twenty milligrams is a small, measured amount of caffeine, which makes it easy to fit into a day. Why caffeine with L-theanine feels different from a cup of coffee is explained in focus without jitters.

The foundation is still the night before. Z-z-Zen combines 1 mg of melatonin with 14 mg of saffron extract, 12 mg of L-glycine and 12 mg of L-theanine. Melatonin contributes to the reduction of time taken to fall asleep. The beneficial effect is obtained by consuming 1 mg of melatonin close to bedtime [10]. Take one strip 20 to 30 minutes before sleep.

The format matters as well. Every Smart Strips formula uses QuickRelease™ film, and the format delivers up to 95% bioavailability, up to 4x faster absorption and up to 30% higher effectiveness than a swallowed tablet, capsule or powder. You can read how on our science page. Smart Strips is the only oral strip brand with a complete functional range, from training and focus to sleep and longevity. See the full range.

When should you see a doctor?

Everyday brain fog lifts when the cause does: after a few good nights, a calmer week, more water. See a doctor if the fog:

• came on suddenly, or after an illness or a new medicine;
• lasts for weeks despite better sleep and habits;
• comes with other symptoms, such as constant tiredness, low mood, weight changes, feeling cold, palpitations, headaches or changes to your periods.

Several health conditions list memory or concentration problems among their symptoms. The NHS names problems with memory and concentration, also called brain fog, as a common symptom of long COVID, the term for COVID-19 symptoms that last longer than 12 weeks [11]. Slow thoughts and memory problems are listed among the symptoms of an underactive thyroid [12]. Iron deficiency anaemia typically brings tiredness and lack of energy [13]. Problems with memory or concentration are a recognised symptom of perimenopause and menopause [14]. And if low mood and difficulty making decisions last most of the day, every day, for more than two weeks, the NHS advises seeing a GP [15].

Some medicines can affect concentration too, so ask your doctor or pharmacist if the fog started with a new prescription. Smart Strips do not diagnose or address any of these conditions. Focus contains caffeine (20 mg per strip) and is not for children or for pregnant or nursing women. Z-z-Zen contains melatonin, is not for children and may cause drowsiness, so do not drive after use. If you take medication or have a medical condition, speak to your doctor before taking any supplement.

How Smart Strips are made

Smart Strips are made in the USA, in an FDA registered, cGMP certified facility certified to NSF/ANSI 455-2. Every formula is tested by independent ISO 17025 accredited laboratories. New to the format? Start with what oral dissolvable strips are.

FAQ

What causes brain fog? In everyday life, most often short sleep over several nights, not drinking enough, stress, constant task switching and long hours without moving. It can also be a symptom of a health condition, so if it is sudden, lasting or comes with other symptoms, see a doctor.

How do you get rid of brain fog? Start with seven or more hours of sleep on a regular schedule. Drink water through the day, work on one task at a time with notifications off and take a ten-minute walk between meetings.

Can dehydration cause brain fog? It can contribute. A meta-analysis of 33 studies found that dehydration impairs attention and executive function, especially once water loss exceeds 2% of body mass.

What is in a Focus strip? 20 mg Alpha-GPC, 20 mg caffeine, 10 mg L-theanine, 10 mg citicoline and 5 mg phosphatidylserine. It dissolves on the tongue in 7 to 30 seconds, with no water.

When is brain fog a reason to see a doctor? When it comes on suddenly, lasts for weeks despite better habits, or comes with other symptoms such as constant tiredness, low mood or weight changes. A doctor can check for causes such as thyroid problems, anaemia, long COVID, menopause or a medicine.

Sources

1. National Heart, Lung, and Blood Institute (NIH). Sleep Deprivation and Deficiency: How Sleep Affects Your Health. Updated 2022. nhlbi.nih.gov/health/sleep-deprivation/health-effects
2. Van Dongen HPA, Maislin G, Mullington JM, Dinges DF. The cumulative cost of additional wakefulness: dose-response effects on neurobehavioral functions and sleep physiology from chronic sleep restriction and total sleep deprivation. Sleep. 2003;26(2):117-126. doi.org/10.1093/sleep/26.2.117
3. Watson NF, Badr MS, Belenky G, Bliwise DL, et al. Recommended amount of sleep for a healthy adult: a joint consensus statement of the American Academy of Sleep Medicine and Sleep Research Society. Journal of Clinical Sleep Medicine. 2015;11(6):591-592. doi.org/10.5664/jcsm.4758
4. Wittbrodt MT, Millard-Stafford M. Dehydration impairs cognitive performance: a meta-analysis. Medicine & Science in Sports & Exercise. 2018. doi.org/10.1249/MSS.0000000000001682
5. Arnsten AFT. Stress signalling pathways that impair prefrontal cortex structure and function. Nature Reviews Neuroscience. 2009;10(6):410-422. doi.org/10.1038/nrn2648
6. Rubinstein JS, Meyer DE, Evans JE. Executive control of cognitive processes in task switching. Journal of Experimental Psychology: Human Perception and Performance. 2001;27(4):763-797. doi.org/10.1037/0096-1523.27.4.763
7. Stothart C, Mitchum A, Yehnert C. The attentional cost of receiving a cell phone notification. Journal of Experimental Psychology: Human Perception and Performance. 2015;41(4):893-897. doi.org/10.1037/xhp0000100
8. Galioto R, Spitznagel MB. The effects of breakfast and breakfast composition on cognition in adults. Advances in Nutrition. 2016;7(3):576S-589S. doi.org/10.3945/an.115.010231
9. Chang YK, Labban JD, Gapin JI, Etnier JL. The effects of acute exercise on cognitive performance: a meta-analysis. Brain Research. 2012;1453:87-101. pubmed.ncbi.nlm.nih.gov/22480735
10. Commission Regulation (EU) No 432/2012 establishing a list of permitted health claims made on foods. eur-lex.europa.eu/eli/reg/2012/432/oj
11. NHS. Long COVID. nhs.uk/conditions/long-covid
12. HSE (Health Service Executive, Ireland). Symptoms of an underactive thyroid. hse.ie/conditions/underactive-thyroid-hypothyroidism/symptoms
13. NHS. Iron deficiency anaemia. nhs.uk/conditions/iron-deficiency-anaemia
14. Cambridge University Hospitals NHS Foundation Trust. Menopause and perimenopause: signs and symptoms. cuh.nhs.uk/rosie-hospital/menopause-and-perimenopause/signs-and-symptoms
15. NHS. Symptoms of depression in adults. nhs.uk/mental-health/conditions/depression-in-adults/symptoms