You’ve tried getting to bed earlier, cutting back on caffeine and switching off your screens before bedtime.. Maybe you've even downloaded a sleep app or bought blackout blinds. But if you're still waking up exhausted or feeling drained throughout the day, more sleep might not be the answer. Persistent tiredness can sometimes be a sign of an underlying health condition that deserves further investigation.
Fatigue is rarely a symptom on its own. It's often your body's way of highlighting an underlying health issue that may otherwise go unnoticed.
While a blood test won't 'fix' your fatigue, it can help identify what's really causing it. The missing step between feeling exhausted and doing something about it is understanding the cause.
There isn't one single test that can tell you why you're tired, instead we use a combination of tests to identify an underlying issue that could be affecting your energy levels and overall wellbeing.
The following blood tests are commonly used to investigate persistent fatigue and help build a clearer picture of what's actually happening inside your body.
| Blood Test | What Does It Check? | How Could It Explain Your Fatigue? |
| Full Blood Count (FBC) | Red and white blood cells and haemoglobin levels | Can identify anaemia, infections and inflammation that may be causing tiredness or weakness. |
Thyroid Function Test (TSH, T3 & T4) | How well your thyroid gland is working | An underactive or overactive thyroid can cause fatigue, weight changes, brain fog and low mood. |
Iron Studies & Ferritin | Your body's iron stores | Low iron levels can leave you feeling exhausted, even if you don't have anaemia. |
Vitamin D | Your vitamin D levels | Vitamin D deficiency is extremely common and may cause tiredness, muscle aches and low mood. |
Vitamin B12 | Your vitamin B12 levels | Low B12 levels can contribute to fatigue, brain fog, weakness and poor concentration. |
| HbA1c | Your average blood sugar levels over the previous 2-3 months | Can help identify pre-diabetes or undiagnosed type 2 diabetes, which commonly causes fatigue. |
Liver Function Tests (LFTs) | How well your liver is functioning | Can identify liver inflammation or strain caused by lifestyle factors, medications or underlying conditions. |
Kidney Function (U&Es) | How effectively your kidneys are working | Kidney problems can develop silently and contribute to tiredness and reduced energy levels. |
C-Reactive Protein (CRP) | Levels of inflammation in the body | Detect inflammation that may contribute to ongoing fatigue |
Cholesterol & Lipid Profile | Your cholesterol and fat levels | Assesses cardiovascular risk and overall health |
Cortisol & Hormone Markers | Hormones that influence stress, metabolism and energy levels | In selected cases, hormone testing may be appropriate depending on your symptoms and medical history. |
Fatigue can have many different causes, so health screens vary in how comprehensive they are — from a general check to a more detailed assessment.
Knowing which option is right for you depends on your symptoms and history which can feel overwhelming.
An Energy & Fatigue Blood Test Package is a good place to start if feeling overly fatigued is your primary issue.
A General health screen is suitable if you:
An Ultimate health screen may suit those who have:
Persistent tiredness isn't a diagnosis-it's a symptom. Understanding the underlying cause is the first step towards finding the right treatment, whether that's correcting a vitamin deficiency, managing thyroid problems or identifying another health condition early.
Book your private health screen today and start understanding what's really behind your tiredness.
Yes. Low vitamin B12, vitamin D and iron are common causes of fatigue and can often be detected through blood testing.
Blood tests can identify many common medical causes of fatigue, although not every cause will appear in blood results.
Iron, vitamin B12 and vitamin D deficiencies are among the most common.
Yes. Thyroid function tests measure hormones like TSH, T3 and T4, which can identify an underactive or overactive thyroid — a common cause of fatigue.
This varies from person to person, but many people book a follow-up screen annually or if new symptoms develop, particularly if previous results were inconclusive.
Blood tests can't directly measure stress or sleep quality, but they can check related markers like cortisol and inflammation, which may be affected by chronic stress.
Not always — fatigue can also result from lifestyle factors like sleep, stress or diet, but persistent or unexplained tiredness is worth investigating with a blood test.
Yes. Iron studies and ferritin levels can be low even before anaemia develops, and this alone can cause fatigue.
A health screen offers multiple tests at once, covering different underlying causes in a single appointment.
Depending on your symptoms, a GP may investigate the most likely causes of fatigue first before considering further testing if required.
A health screen saves time by looking at multiple potential causes and deficiencies in one appointment providing a broader picture of your overall health.
If you’ve previously had a blood test that gave you the all-clear but you still feel tired, it helps to rule out possible causes and catch what wasn’t checked before.
A member of our team will be in touch with you to discuss your requirements.
