4 / Brain Fog and Poor Sleep: What Is Actually Worth Checking?

We have spent the first three articles understanding why sleep, stress and brain fog often appear together, identifying the biggest disruptors and looking at how to rebuild better sleep and long-term brain resilience. But there comes a point when lifestyle changes are no longer the whole answer.

Perhaps you have stabilised your sleep schedule, reduced alcohol, moved caffeine earlier, addressed obvious stressors and improved your nutrition and movement. Yet you still wake exhausted. Perhaps the brain fog is becoming more noticeable rather than less, or your concentration and memory feel significantly different from what is normal for you.

This is where I want us to stop adding supplements and start asking better questions. Persistent fatigue, poor sleep and cognitive symptoms deserve investigation when the obvious explanations no longer fit. And just as we have done throughout this website, we test because we are trying to answer a specific question, not because a laboratory offers an impressive panel.

Start with a full blood count and iron status

A full blood count, or FBC, is a sensible starting point because anaemia can cause fatigue, weakness, reduced exercise tolerance and difficulty concentrating.

But haemoglobin alone does not tell us everything about iron status.

Ferritin gives us information about stored iron, and iron stores can become depleted before significant anaemia develops. This is particularly relevant during perimenopause if periods have become heavier or more prolonged.

When the picture is unclear, ferritin can be considered alongside serum iron, transferrin or total iron-binding capacity and transferrin saturation. Ferritin also behaves as an acute-phase protein and may rise with inflammation, so it should not always be interpreted in isolation.

Iron matters to this particular series for another reason. Low iron stores can be associated with restless legs syndrome, which can seriously disrupt sleep. If you experience an uncomfortable urge to move your legs when resting, particularly in the evening or at night, iron status becomes even more relevant.

If iron deficiency is found, however, the investigation should not end with an iron supplement. We also need to understand why the iron is low.

Check vitamin B12 when the symptoms fit

Vitamin B12 deficiency can produce fatigue and neurological symptoms, including cognitive changes, numbness, tingling, balance problems and other nervous-system abnormalities.

Importantly, B12 deficiency does not always present with obvious anaemia. A normal full blood count therefore does not necessarily exclude it.

Risk becomes more relevant with certain dietary patterns, autoimmune gastritis, gastrointestinal surgery and conditions that impair absorption. Long-term use of medications including metformin and proton pump inhibitors can also increase the risk in some people.

Initial investigation commonly includes serum B12 or active B12. If the result is borderline but clinical suspicion remains, additional testing such as methylmalonic acid, or MMA, can sometimes help clarify whether there is a functional deficiency.

This is a good example of why I prefer testing before supplementing. Taking high-dose B12 can alter the blood result and make the original picture more difficult to interpret.

Thyroid dysfunction can look remarkably like menopause

An underactive thyroid can cause fatigue, cognitive slowing, low mood, constipation, cold intolerance, dry skin, hair changes and changes in weight.

You can immediately see the problem.

Many of those symptoms overlap with complaints commonly attributed to menopause. That does not mean every tired woman needs an enormous thyroid panel, but persistent symptoms deserve enough investigation to avoid automatically blaming hormones.

For suspected primary thyroid dysfunction, TSH is usually the appropriate starting test, with free T4 added or interpreted according to the result and clinical situation. Additional thyroid investigations may be appropriate when there is a specific reason for them.

And remember that supplements matter here too. High-dose biotin, often found in hair and nail supplements, can interfere with some laboratory assays and produce misleading thyroid results. Tell your healthcare professional what you are taking before testing.

Look at glucose and metabolic health

Poor metabolic health can influence energy, vascular health and long-term cognitive health, so this is another area worth assessing rather than guessing.

Fasting glucose and HbA1c can identify abnormal glucose regulation and help screen for prediabetes and diabetes. HbA1c gives us information about average glucose exposure over approximately the previous two to three months rather than one moment in time.

In selected cases, I also like to look at fasting insulin alongside glucose, particularly when there are other signs of insulin resistance such as increasing abdominal fat, high triglycerides, low HDL, hypertension, previous gestational diabetes or PCOS. Fasting insulin is not, however, a diagnostic "brain fog test."

The wider metabolic picture matters too. Blood pressure and a lipid profile, including LDL cholesterol and triglycerides, are relevant to long-term vascular and brain health.

This is not because slightly elevated cholesterol explains why you forgot somebody's name yesterday. It is because the blood vessels supplying your brain deserve the same attention as those supplying your heart.

Vitamin D can be checked when there is a reason

Vitamin D deficiency can be associated with muscle weakness and other health problems, but fatigue and brain fog are so nonspecific that they cannot diagnose vitamin D deficiency.

Testing 25-hydroxyvitamin D makes sense when there are risk factors for deficiency, bone-health concerns or other clinical indications.

If you are deficient, correct it appropriately. But once again, more is not automatically better. Driving vitamin D concentrations increasingly higher is not a treatment for unexplained brain fog.

The aim of testing is to identify and correct a genuine problem, not optimise every blood marker to an arbitrary internet target.

Don't forget liver function, kidney function and electrolytes

Persistent fatigue or cognitive changes sometimes require us to widen the view beyond the obvious menopause-related possibilities.

A basic biochemical assessment may include renal function, creatinine, eGFR, sodium and potassium, with additional electrolytes where appropriate. Significant disturbances can affect energy, neurological function and overall wellbeing.

Liver function tests may also be useful depending on symptoms, medications, alcohol intake and medical history. The liver is central to metabolism and the processing of many medications and endogenous compounds, while significant liver dysfunction can eventually affect cognition.

These tests are not specifically "brain fog markers." They are part of making sure we are not overlooking a broader medical problem.

Do you need your cortisol tested?

Usually not simply because you feel stressed, tired or wake during the night.

Cortisol has a normal circadian rhythm and changes throughout the day. It is influenced by sleep, illness, exercise, psychological stress and numerous other factors. A single random cortisol result therefore tells us very little about why you feel overwhelmed or why you woke at 3 am.

Cortisol testing becomes medically important when there is genuine suspicion of a disorder of cortisol production, such as adrenal insufficiency or Cushing syndrome. Those conditions have specific clinical presentations and require appropriate diagnostic testing.

This is very different from assuming that chronic stress has given you "adrenal fatigue."

The adrenal glands do not generally become tired because you have had a difficult year. Chronic stress can profoundly affect sleep, mood, behaviour and physiology, but "adrenal fatigue" is not a recognised medical diagnosis.

We can take stress seriously without inventing an adrenal disease to explain it.

Do you need your menopause hormones checked?

Usually not because of brain fog or poor sleep alone.

During perimenopause, FSH and estradiol can fluctuate considerably, which means one blood result may provide a snapshot without reliably representing what is happening across the entire transition. In women over 45 with typical cycle changes and menopausal symptoms, perimenopause is generally identified clinically rather than through repeated hormone panels.

Hormone testing may be appropriate in particular circumstances, particularly when the diagnosis is uncertain, symptoms occur unusually early or another endocrine problem is being considered.

But checking estrogen, progesterone, testosterone, DHEA and cortisol because you are tired, stressed and forgetful rarely gives us a complete explanation.

The question should always come first: What exactly are we trying to diagnose?

Blood tests cannot tell us whether you have sleep apnoea

This may be one of the most important sections of the entire series.

You can have immaculate blood results and still feel exhausted every morning because your breathing is repeatedly disturbed while you sleep.

Obstructive sleep apnoea causes repeated narrowing or closure of the upper airway during sleep. Oxygen levels may fall and the brain repeatedly produces brief arousals to restore breathing. You may not remember any of this happening.

Women can present with snoring and daytime sleepiness, but they may also report insomnia, morning headaches, fatigue, low mood and cognitive problems. Risk increases after menopause, and factors such as body weight and upper-airway anatomy also influence risk.

If you snore loudly, wake choking or gasping, have witnessed pauses in breathing, wake with headaches or consistently feel unrefreshed despite apparently sufficient sleep, a sleep assessment may tell us far more than another blood panel.

Depending on the situation, this may involve a home sleep study or an overnight laboratory sleep study.

Restless legs can quietly destroy sleep too

Restless legs syndrome produces an uncomfortable urge to move the legs, typically when resting and particularly in the evening or at night. Movement temporarily relieves the sensation.

It can make falling asleep extremely difficult and can coexist with periodic limb movements during sleep, which may further disrupt sleep quality.

Iron status is important because iron deficiency can contribute to restless legs symptoms. Certain medications and other medical conditions can also be involved.

If your legs feel restless, crawling, uncomfortable or impossible to keep still when you get into bed, mention it rather than simply saying that you have insomnia. The detail changes the investigation.

Review your medications and supplements

This is easily overlooked.

Some medications can cause sedation, while others can contribute to insomnia, restlessness or cognitive changes. Antihistamines, certain antidepressants, sedatives, pain medications and anticholinergic drugs are among the many medications that can potentially affect alertness, sleep or cognition.

Timing can matter too. A medication may be necessary but work better for you at a different time of day, depending on what it is and how it affects you.

Supplements deserve the same review. "Natural" does not mean neurologically inactive. Some products contain stimulants, sedating compounds or multiple ingredients that can interact with medications.

Bring the entire list to a medication review, including the supplements you bought yourself. Everything you take counts.

Alcohol deserves an honest look

If you are struggling with sleep and cognition, alcohol should be part of the assessment.

Alcohol can fragment sleep, worsen sleep apnoea and contribute to daytime fatigue. Higher alcohol consumption can also affect mood, blood pressure, liver function and cognitive health.

The difficult part is that alcohol often becomes intertwined with stress. A glass of wine provides a clear boundary between work and evening, helps you feel temporarily relaxed and may make falling asleep easier.

But if you are waking repeatedly in the second half of the night and feeling foggy the next morning, it is worth finding out what happens without it.

A few alcohol-free weeks can function as a very useful personal experiment.

Depression and anxiety can present as cognitive problems

Depression does not always look like sadness. Anxiety does not always look like panic.

Both can affect attention, working memory, processing speed, motivation and sleep. A woman may therefore describe herself as forgetful or mentally slow when part of the problem is that her brain is struggling to concentrate sufficiently to encode information in the first place.

This does not mean cognitive symptoms should be dismissed as psychological. It means mental health is part of brain health.

If low mood, loss of pleasure, persistent anxiety, emotional numbness, excessive worry or major changes in motivation accompany the cognitive symptoms, they deserve proper assessment alongside the physical investigation.

Hearing and vision deserve more attention than they get

This may seem like an odd addition to an article about brain fog, but sensory health matters to cognitive function.

If you cannot hear information clearly, the brain has to work harder to process conversation, and information you never accurately heard cannot be remembered properly later. Hearing loss is also recognised as an important modifiable risk factor associated with dementia.

Vision problems can similarly increase cognitive load and affect everyday functioning.

So if you constantly ask people to repeat themselves, struggle to follow conversations in noisy environments or haven't had your hearing and vision checked for years, include them in your midlife health assessment.

Brain health is not confined to what happens inside the skull.

When does brain fog need a proper cognitive assessment?

This is where we need to distinguish frustrating but relatively mild cognitive changes from something more concerning.

Forgetting a word and remembering it later, occasionally losing your keys or walking into the kitchen and forgetting what you wanted are common experiences, particularly when you are tired, distracted or stressed.

I become more concerned when cognitive changes are progressive, noticeably worsening or interfering with everyday independence. Repeatedly getting lost in familiar places, struggling to manage finances you previously handled easily, being unable to follow familiar procedures, significant changes in judgement or personality, repeatedly asking the same questions or cognitive changes noticed by family members deserve medical assessment.

A clinician may use a screening tool such as the Montreal Cognitive Assessment, or MoCA, as part of an evaluation. But a screening score is not a diagnosis of dementia. Cognitive assessment also considers medical history, neurological examination, medications, mood, sleep and other possible causes, with brain imaging or specialist assessment when indicated.

Do not diagnose yourself from an online memory test.

Sudden cognitive change is different

There is one distinction I want to make very clearly.

Gradual brain fog developing alongside perimenopause, poor sleep and stress is very different from sudden confusion, difficulty speaking, facial weakness, weakness or numbness on one side of the body, severe sudden headache or abrupt changes in vision or balance.

Those symptoms can indicate a neurological emergency such as stroke and require urgent medical attention.

Similarly, sudden severe confusion, known as delirium, can occur with infections, medication effects, metabolic disturbances and other acute illnesses and requires prompt assessment.

Not every cognitive change belongs in a menopause conversation.

Brain fog and poor sleep: what would I actually check?

For persistent fatigue, poor sleep or brain fog, a sensible starting assessment may include a full blood count, ferritin with fuller iron studies where appropriate, vitamin B12, folate when indicated, TSH with appropriate thyroid testing, fasting glucose and HbA1c, a lipid profile, blood pressure, renal function and electrolytes, and liver markers. Vitamin D may be useful where there is a reason to suspect deficiency or assess bone health.

From there, testing should follow the symptoms rather than expanding automatically. Restless legs makes iron status particularly relevant. Snoring and unrefreshing sleep may point towards a sleep study. Persistent mood symptoms may require mental-health assessment. Progressive cognitive changes require proper cognitive and neurological evaluation.

And medication, supplement, alcohol, hearing and vision reviews may sometimes provide more useful information than another laboratory test.

The aim is not to prove that every marker is perfect. It is to find anything that could realistically be contributing to the symptoms and that we can actually do something about.

What I want you to take away from this series

Sleep, stress and brain fog can absolutely change during the menopause transition, but that does not mean every symptom should automatically be attributed to menopause. Start by understanding the pattern, address the biggest sleep and stress disruptors, build the foundations that protect your brain and metabolic health, and investigate when symptoms persist.

Most importantly, brain fog is a symptom, not a diagnosis. If your brain feels different, listen to that information without immediately assuming the worst.

Sometimes the answer is sleep. Sometimes it is iron, B12, thyroid function, metabolic health, medication, mood or sleep apnoea. And occasionally, cognitive changes need a deeper neurological investigation. The goal is neither to panic nor dismiss it as "just menopause." The goal is to understand what your brain is telling you.

You can explore more articles, free and paid resources, my book and programmes in the Sleep, Stress & Brain Fog section of Feel Good Menopause.