Brain fog: what it is, and what actually helps
Brain fog is not a diagnosis. It is a description — of thinking that feels slower, hazier and more effortful than it used to. There is no test for it and no medicine that treats it, because it is a symptom rather than a disease. What helps is working out which of a small number of common causes is behind it, and dealing with that.
That is the short answer. The longer one is worth reading, because the causes are more ordinary than most people fear.
What brain fog actually feels like
People describe it in very consistent ways. You walk into a room and cannot retrieve why. You read the same paragraph three times. A word you have used your whole life sits just out of reach. Conversations that used to be easy now take effort, and by four in the afternoon you have nothing left.
None of that is unusual, and on its own none of it indicates disease. What makes it worth attention is change — thinking that is meaningfully different from your own normal, sustained over weeks rather than days.
Two things are worth establishing before anything else. Brain fog is a real experience, not imagination or laziness. And it usually has a mundane, identifiable and addressable explanation.
The common causes after 45
These are the ones worth working through first, because they are common, checkable, and in most cases fixable.
Sleep that is broken rather than short
This is the place to start, and the most commonly missed — because people report their hours, not their quality. Seven hours of fragmented sleep does not do what seven hours of consolidated sleep does. Attention and working memory are among the first functions to suffer when deep sleep is disrupted.
From the mid-forties on, sleep quality changes for reasons that have nothing to do with effort or discipline: waking more often, waking earlier, and — for women — hormonal shifts that disturb the night directly.
Perimenopause and menopause
For a great many women in their forties and fifties, brain fog arrives alongside disturbed sleep, night sweats and mood changes. It is one of the symptoms women find most alarming, and one of the least discussed.
The International Menopause Society published a white paper specifically on this, written to help clinicians counsel women through it. Its framing is worth borrowing directly: cognitive changes through the menopause transition are common, women frequently worry they represent the beginning of something more serious, and a central part of good care is normalising the experience — explaining what the changes are, how long they tend to last, and how severe they typically are. Maki & Jaff, Climacteric, 2022 (via PubMed).
Fluctuating oestrogen appears to affect cognition both directly and indirectly — indirectly, and probably more importantly, by disrupting sleep. Women reporting the worst cognitive symptoms in perimenopause tend also to report the worst nights.
Worth saying plainly: brain fog in perimenopause is common, it is recognised, and for most women it settles. It is not early dementia. If that is the worry, say so to your GP rather than sitting with it — it is a conversation worth having properly, not one to have with a search engine at 2am.
More in our guide to perimenopause in your 40s.
Thyroid, iron and B12
Three of the most common things a blood test finds, and all three can present as foggy thinking and fatigue.
- Underactive thyroid — slowed thinking, fatigue, feeling cold, weight change.
- Low iron or ferritin — common in women still menstruating, including irregularly through perimenopause.
- Low vitamin B12 — absorption declines with age, and clinical guidance identifies specific risk factors including metformin use beyond four months, proton-pump inhibitors or H2 blockers beyond twelve months, a vegan or strict vegetarian diet, and being over 75. Both metformin and reflux medicines are very widely prescribed in this age group. Langan & Goodbred, American Family Physician, 2017 (via PubMed).
These matter because they are simple to check and straightforward to correct once identified. They are also why guessing at supplements is the wrong first move. If low B12 is the cause, B12 helps because a deficiency has been corrected. If it isn't, it does nothing — the same guidance notes that B12 given to people without a deficiency does not alter cognitive decline. You cannot tell which situation you're in without testing.
Medication
More common than people expect. Antihistamines, some blood pressure medicines, sleeping tablets, some antidepressants and others can dull thinking, particularly in combination. If your fog began within a few weeks of a new prescription or a dose change, that is the first thing to raise with your prescriber. Do not stop anything on your own.
Alcohol
Even at levels most people consider moderate, alcohol reduces sleep quality — most sharply in the second half of the night. Tolerance for it tends to drop with age. It is one of the more reliable changes to test on yourself.
Stress and low mood
Sustained stress consumes the same working-memory capacity that concentration needs. Depression frequently presents in mid-life as fog and fatigue rather than as sadness, which is why it is so often missed. If low mood or loss of interest is part of the picture, treat that as the main issue.
What genuinely helps
In rough order of what makes the most difference:
- Fix the sleep first. Nothing else on this list produces as much improvement. Consistent bed and wake times, a cool dark room, no alcohol close to bed, no screens in the last hour. Dull advice. It works.
- Get the simple tests done. Thyroid, iron and ferritin, B12, and depending on your history HbA1c. One blood test settles several questions at once.
- Review the medicine list with your doctor or pharmacist, particularly if you take three or more.
- Move daily. Physical activity is among the modifiable factors consistently identified for brain health in mid-life and beyond. Walking counts.
- Cut the alcohol back and see. Two weeks is enough to tell.
- Eat properly and regularly. Wildly swinging blood glucose produces exactly this pattern of afternoon fog.
- Address the perimenopause directly if that is the context. Options exist and are worth discussing with your GP.
Where supplements sit in this
Lower down the list than the internet suggests — and we say that as a company that makes them.
A supplement corrects a shortfall. If a nutrient shortfall is causing your symptoms, correcting it helps. If it isn't, it doesn't, and no formulation changes that arithmetic. The useful sequence is test, identify, then correct. Not buy, hope, repeat.
Where supplements do earn their place for adults over 45 is in the ordinary background maintenance of nutrients that genuinely become harder to get enough of after mid-life — and, for people whose nights are the problem, in supporting sleep quality, since sleep is where most brain fog is actually made.
When to see your doctor
Please make an appointment if:
- The change came on quickly, or is getting steadily worse
- Other people have noticed it, not only you
- You are getting lost in familiar places, or losing words rather than pausing for them
- There are other neurological symptoms — weakness, numbness, changes in vision, unsteadiness
- Your mood is low, or you have lost interest in things you used to enjoy
- It followed a head injury, a serious illness, or a new medicine
- It is affecting your work or your safety
Bring a written list. When you have been foggy for months, the fog itself will take the appointment from you.
Frequently asked questions
What does brain fog feel like?
Brain fog feels like thinking through treacle — slower recall, difficulty holding attention, losing words mid-sentence, and mental fatigue that arrives earlier in the day than it used to. It is a description of an experience rather than a medical diagnosis, and it is not the same as memory loss.
How do you get rid of brain fog?
By identifying and addressing the cause. Most commonly that means improving sleep quality, checking thyroid function, iron and vitamin B12 with a blood test, reviewing medications with your doctor, reducing alcohol, and addressing stress or low mood. There is no single treatment for brain fog because it is a symptom of several different things.
Is brain fog a normal part of menopause?
Yes. Difficulty concentrating and word-finding problems are commonly reported through perimenopause and menopause, and are thought to relate both to fluctuating oestrogen and to the disturbed sleep that often accompanies it. The International Menopause Society's guidance for clinicians emphasises normalising these changes for women. For most women they settle. If you are concerned, discuss it with your GP.
Can a vitamin deficiency cause brain fog?
Low vitamin B12 and low iron are both associated with fatigue and poor concentration. Clinical guidance flags particular B12 risk factors including metformin use beyond four months, long-term reflux medication, a vegan or strict vegetarian diet, and being over 75. A blood test is the only way to know — and B12 taken without a deficiency has not been shown to alter cognitive decline.
Is there a test for brain fog?
There is no test for brain fog itself. There are tests for its common causes: thyroid function, full blood count, ferritin, vitamin B12, and blood glucose. Your GP may also do a brief cognitive assessment if it is warranted.
Is brain fog a sign of dementia?
In most people, no. Brain fog is far more commonly caused by sleep, hormones, nutrient deficiencies, medication or stress. The features that warrant prompt medical assessment are steady worsening over months, difficulty with familiar routes and tasks, and changes other people notice before you do. If you are worried, see your doctor — that is what the appointment is for.
Lifeguard Health makes NZ-made, doctor-formulated supplements for adults 45+. If sleep is the part of this picture you want to work on, see our guide to magnesium for sleep, or browse our healthy ageing range.
This article is general information and is not a substitute for individual medical advice. If you are concerned about your health, see your own doctor.
