Cognitive health
Brain fog
Difficulty concentrating, losing words, reading the same paragraph three times. It is real, it is common, and it is not the same thing as dementia — though the fear that it might be is often what brings people in.
By Dr Andrew Greenland· Reviewed
At a glance
Greenland Medical is a doctor-led practice in Twickenham, London, where Dr Andrew Greenland investigates persistent brain fog, in person or online. Most brain fog has a findable cause: sleep, thyroid, iron or B12, inflammation, post-viral illness or medication. The work is finding which, and treating it.
- Who you see
- Dr Andrew Greenland, GMC-registered (4419909), at every appointment
- Where
- The Maris Practice, Twickenham TW1 3HQ, and online across the UK
- Assessment
- Full history and examination, a cognitive screen where memory is a concern, and blood work guided by the history
- Fees
- Initial consultation £880 (120 minutes), follow-up £440. Testing is separate, with a written estimate first
- First appointment
- Usually within two to three weeks
- If it is memory
- Where the picture suggests early cognitive decline, the dementia and Alzheimer’s assessment applies instead
- Next step
- A free 15-minute discovery call
First, what it usually is not
Brain fog in someone in their thirties or forties is very rarely early dementia. It is far more often the cognitive expression of something systemic: disrupted sleep, thyroid dysfunction, iron or B12 deficiency, perimenopause, chronic inflammation, post-viral illness, or the aftermath of prolonged stress.
That distinction matters, because it changes what is worth investigating. It also tends to be a relief, and people are often carrying more anxiety about this than they let on.
The usual contributors
Sleep is the one most often dismissed and most often relevant. Untreated sleep apnoea in particular produces exactly this picture and is frequently missed.
Then thyroid function, iron studies and B12, blood glucose regulation, hormonal change, and inflammatory markers. In some people gut function and histamine handling are part of it. Post-viral fatigue, including after COVID-19, commonly presents this way.
The aim is to work out which of these apply to you rather than treating brain fog as a condition in its own right, because it is not one.
Common questions
When should I be worried it is something more?
Progressive worsening over months, difficulty with familiar tasks rather than just concentration, getting lost in familiar places, or others noticing before you do. Those warrant proper assessment, and I would want you seen appropriately rather than reassured.
Is this the same as long COVID?
Post-viral cognitive symptoms overlap heavily with what people call brain fog, and COVID-19 is a common trigger. The investigation is broadly similar; recovery is often slower and needs patience.
Can it be fixed?
Often it improves substantially when the underlying contributor is identified and treated, particularly where sleep, thyroid or deficiency is involved. Where no single cause emerges, progress tends to be slower and more incremental. I will be honest about which situation yours looks like.
Related
Discuss your case with Dr Greenland
A short discovery call is the usual starting point. It costs nothing, and it is the fastest way to find out whether this approach fits your situation.