What to do when your blood tests keep coming back normal
If you’ve been in asking yourself, ‘Why do I feel tired all the time?’, your’re in good company. It’s one of the common reasons people come to see a GP, and most of the time there is a simple explanation. But being tired all the time is different. If you have felt wrung out for months, and you are wondering why when you have been told, again, that your blood tests are normal, this article is for you. We see it in clinic constantly.
The most common cause of being tired all the time is poor quality sleep, not a shortage of hours in bed. After that, the causes I find most often are undiagnosed obstructive sleep apnoea, perimenopause and menopause, thyroid problems, low iron stores, and depression, anxiety or burnout. Persistent exhaustion is a symptom with a cause, and normal blood tests do not mean there is nothing to find.
I’m Dr Alice Scott, a GP at Essex Private Doctors, where I lead our sleep clinic and work as a BMS-accredited menopause specialist. The patient I meet most often in this situation is a woman in midlife who has been to her GP three or four times about exhaustion, been tested each time, been told everything is normal, and quietly stopped going. She has picked up the unspoken message: this is just life. You’re busy. What did you expect?
Being exhausted is not an inevitable part of being in your forties. Here is how we work out what is actually going on:
First: are you sleepy, or are you fatigued?
These words get used interchangeably, but they point in different directions, and the distinction is the most useful thing you can bring to your appointment.
Sleepy means you are genuinely falling asleep during the day: napping, nodding off in a chair, dropping off as a car passenger. This points strongly towards a sleep disorder, and obstructive sleep apnoea in particular.
Fatigued means you feel unwell and wrung out but can push through the day, and often cannot nap even when you are desperate for rest. This opens a broader field: hormones, deficiencies, thyroid, mood.
The causes of constant tiredness we consider:
Poor sleep quality
Time in bed is not the same as restorative sleep, which is why people rule sleep out too early: they had eight hours, so it can’t be that. It very often is. Insomnia, sleep deprivation and untreated sleep disorders are all distinct problems with different solutions, and none of them show up on a blood test. My rule of thumb: if you have had repeated blood tests for tiredness that keep coming back normal, it is your sleep that needs investigating.
- Obstructive sleep apnoea
This is the diagnosis I am most concerned not to miss: it causes real daytime sleepiness, it is very treatable, and untreated it threatens your heart and your safety to drive. Most people picture an overweight man snoring like a chainsaw. After menopause, I see it just as often in women, because falling hormone levels reduce muscle tone in the throat. Women also rarely present with the textbook picture: they come with insomnia, unrefreshing sleep, morning headaches, low mood, anxiety, night-time trips to the loo and fatigue, all of which get blamed on menopause for years. A home sleep study, worn in your own bed, settles it.
- Menopause and perimenopause fatigue
Falling oestrogen destabilises the brain systems controlling temperature, mood and the sleep-wake cycle, bringing night sweats and lighter sleep. Progesterone, which is naturally calming, becomes erratic and declines, adding restlessness and anxiety. Cortisol then rises in the early hours to prepare you to wake, so a nervous system already running hot tips you into full wakefulness at 3am. Poor sleep in menopause leads months of broken nights and days spent running on empty.
- Thyroid problems
Thyroid dysfunction disturbs sleep in both directions. An overactive thyroid leaves you wired and unable to settle. An underactive one, including autoimmune Hashimoto’s, produces fragmented, non-restorative sleep alongside the classic sluggishness. It is easily tested and easily treated, which is exactly why it should never be assumed.
- Low iron, and other deficiencies
Low iron is very common in women, and B12, folate and vitamin D matter too. But here is the part that frustrates patients most, rightly. Ferritin, which reflects your iron stores, is the clearest example of a number that can be reported as normal while still being wrong for you: many women feel considerably better with a ferritin between roughly 50 and 90, yet a result at the very bottom of the range gets waved through. Told only that it was normal, they believe iron has been ruled out when it has not been optimised at all.
- Low testosterone in men
Men are not exempt from any of this. Low testosterone causes genuine fatigue, and I most often find it alongside obstructive sleep apnoea, where the two compound each other. If a man in his forties or fifties is exhausted and flat, both belong on the list.
- Depression, anxiety and burnout
This is physical, not just psychological. Changes in serotonin, noradrenaline and dopamine directly affect motivation and physical movement, so your limbs genuinely feel heavier. Low mood also strips out REM sleep, the stage your brain needs for emotional processing, so you wake less resilient and the next night is worse. I rarely find it useful to ask whether someone is tired because they are low or low because they are tired. Usually both are true, and the practical question is where we break the loop.
- The less common causes worth excluding
Uncontrolled diabetes, coeliac disease, heart failure, post-viral and post-COVID fatigue, and medication side effects, which are common and easily reversible once spotted.
Is “adrenal fatigue” real?
No. Adrenal fatigue is not a recognised medical diagnosis, and your adrenal glands do not become exhausted and stop producing cortisol because life has been stressful. What genuinely happens, and what I think people are reaching for with the term, is that the stress response system becomes dysregulated: the timing and pattern of cortisol release shifts, which affects your sleep, your energy through the day and how you feel on waking.
The exhaustion is completely real. The label is the problem, and my objection is practical rather than pedantic. I have met patients who spent a year and a great deal of money on adrenal support supplements while an undiagnosed thyroid problem, iron deficiency or sleep apnoea went untreated.
When is tiredness serious? Red flags to act on
See a doctor promptly if your fatigue comes with any of the following:
- Unexplained weight loss
- Unexplained sweating, particularly at night
- Bone pain
- Breathlessness, chest pain or swollen ankles
- Falling asleep while driving
Why “your bloods are normal” is not an answer
Most people who come to me have had some blood tests. Very few have had the right ones, interpreted properly, and almost nobody has had them explained.
Three things go wrong. The panel is often narrower than it should be, so whole categories of cause are never examined. The results are then reduced to a single word, normal, which only means your figure sits inside a population range. And a one-off reading hides the trajectory: a number that has halved since last year can still read as normal while telling you something important.
How we investigate fatigue at Essex Private Doctors
We begin with an unhurried, detailed history, because that is what tells me where to look. Then the right investigations for your particular picture, taken here in clinic, with results back in days rather than months and explained to you properly: what each number means, how it compares with your previous results, and what happens next. From there, a home sleep study if sleep apnoea is possible, face-to-face CBT-I if insomnia is driving it, shared care with our menopause clinic where hormones are a factor, or referral to precisely the right specialist, first time.
GPs are the last true generalists in medicine. That means we can assess your sleep, hormones, bloods, heart and mental health as one picture rather than in separate silos, which is exactly what unexplained fatigue requires.
One patient I think of often is a gentleman in his sixties who had struggled with fatigue and anxiety for years, with bloods that kept coming back normal. A sleep study showed obstructive sleep apnoea. He is now on treatment. Years of exhaustion, and the answer was one test nobody had arranged.
Frequently Asked Questions
As a middle-aged woman, why am I always tired and have no energy?
In midlife women, the usual explanations are poor sleep quality, perimenopausal or menopausal hormone changes, low iron stores, thyroid problems and undiagnosed sleep apnoea, which is far more common in women after menopause than most people realise. Often several are involved at once.
What deficiency causes tiredness and fatigue?
Iron is the most common, and it is best assessed by ferritin rather than haemoglobin alone. B12, folate and vitamin D also matter. A result at the bottom of the reference range may be reported as normal while still being too low for you to feel well.
Can stress and anxiety make you physically tired?
Yes. Stress and low mood alter serotonin, noradrenaline and dopamine, which affect motivation and physical movement, and they disrupt the REM sleep that supports emotional resilience. The physical exhaustion is real, not imagined.
I’ve had blood tests and they were normal. What now?
Ask which tests were done and what the actual numbers were. Normal only means your result falls inside a population range, not that it is right for you, and a single reading tells you nothing about which direction it is moving. If the panel was narrow, or nobody has assessed your sleep, the investigation is not finished.
How long is it normal to feel tired before seeing a doctor?
If exhaustion has lasted more than a few weeks without an obvious explanation, or it is stopping you doing things you want to do, it is worth investigating. Sooner if you have any of the red flag symptoms above.
Is being tired all the time just my age?
No. Energy changes across life, but persistent exhaustion is a symptom, not a birthday.
You deserve an actual answer
Most causes of constant fatigue are treatable, and many are straightforward once identified. If you have been tired for months, told your bloods are normal, and left it there, book an assessment and let’s find out why.
About the author
Dr Alice Scott MBChB MRCGP is a GP at Essex Private Doctors in Brentwood, Essex. She leads the practice’s sleep clinic, holds additional postgraduate training in the management of sleep disorders, and is a BMS-accredited menopause specialist and Clinical Lead of the Essex Menopause Clinic.
Essex Private Doctors provides comprehensive fatigue assessment, in-house blood testing, home sleep studies and face-to-face CBT-I in Brentwood, Essex. Serving Chelmsford, Billericay, Basildon, Romford, Colchester, Southend, Harlow and surrounding Essex areas, with easy access from North and East London via the Elizabeth line.
