Fatigue that doesn't shift with a good night's sleep is worth investigating. It's one of the most frequent complaints GPs hear, and while the causes are many, a targeted set of blood tests can rule out — or identify — some of the most common physical ones relatively quickly.
Why blood tests for tiredness?
Tiredness has dozens of potential causes, from sleep problems and stress to nutritional deficiencies and underlying health conditions. Many of the physical causes show up clearly in blood results. That's what makes a blood screen a sensible first step: it's non-invasive, quick, and can either give you answers or meaningfully narrow things down.
A GP can look at your symptoms, medical history and lifestyle alongside the results — that context matters as much as the numbers themselves.
Which tests are most relevant?
The core panel for someone presenting with persistent tiredness typically includes:
- Full blood count (FBC) — checks for anaemia (low red blood cells or haemoglobin), which is a very common cause of fatigue
- Iron studies — ferritin (stored iron), serum iron and transferrin saturation; iron deficiency can cause tiredness even before anaemia develops
- Vitamin B12 and folate — deficiency in either can cause significant fatigue and is correctable once identified
- Vitamin D — low vitamin D is extremely common in the UK, particularly through winter, and is strongly associated with low energy and low mood
- Thyroid function (TSH, T4) — an underactive thyroid is a classic, often missed cause of exhaustion, weight changes and feeling cold
- Blood glucose / HbA1c — undiagnosed or poorly controlled diabetes can cause persistent tiredness
- Kidney and liver function — a general marker of how well these organs are working
What our blood screens include
At Northwest Health, our blood screens are designed to give a broad view rather than a single isolated result. Our Silver screen (£200) covers the key markers for tiredness including FBC, iron, B12, folate, vitamin D, thyroid, glucose and metabolic panels. Our Gold (£350) and Platinum (£500) screens go further if you want a more comprehensive picture.
All results are reviewed by a GP, not just returned as numbers. That means you'll receive an explanation of what your results mean and what, if anything, needs to happen next.
Are these tests diagnostic?
It's important to be clear: a blood screen is a screening tool, not a diagnosis. A normal result doesn't mean there's nothing wrong — some causes of tiredness won't show in blood tests. An abnormal result is a starting point for further conversation with a doctor, not a conclusion on its own.
What if my results are normal?
If blood tests come back within normal ranges, that's actually useful information. It helps focus the conversation toward other possible causes — sleep quality, stress, mental health, or lifestyle factors — and avoids unnecessary further investigation.
You don't need a referral to book a blood test at Northwest Health, and results are typically available within a few working days.
Find out more about our blood tests →
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