Fatigue & Tiredness Blood Test
Fatigue blood test in Plymouth
Tired all the time? Our fatigue blood test panel in Plymouth is our most popular test – it covers 13 of the most common reversible causes of persistent tiredness in a single appointment. If you’re suffering from unexplained fatigue, brain fog, low energy, and poor sleep quality despite getting what should be enough sleep, this panel finds the cause. This comprehensive panel tests a Full Blood Count, full Iron Studies, a complete Thyroid panel with Free T3 and Antibodies, Vitamin B12, Folate, Vitamin D, HbA1c, Insulin, C-peptide, Magnesium, Kidney Function, Calcium and High-Sensitivity CRP – everything that commonly causes fatigue but is easily fixed once identified.
Why this test matters
Persistent fatigue is one of the most frustrating symptoms to live with – it affects every part of life, from work performance to exercise to mental health. Many people are told “it’s just stress” or “get more sleep,” but often there’s an underlying medical cause. Low iron, low thyroid, B12 or folate deficiency, vitamin D deficiency, low magnesium, kidney problems, insulin resistance and undiagnosed diabetes all cause fatigue that has nothing to do with how much you sleep. This panel tests all of these in one go, saving time and ensuring nothing is missed. Most people are shocked when their fatigue resolves after treating an identified deficiency.
What this test measures
This panel combines 13 test groups into one comprehensive fatigue investigation, covering blood cells, iron, thyroid, vitamins, blood sugar regulation, kidney function and inflammation.
| Test component | What it measures | Why fatigue happens when it’s abnormal |
|---|---|---|
| Full Blood Count (FBC) | Red blood cells, white blood cells, platelets, haemoglobin | Anaemia (low red blood cells or haemoglobin) prevents oxygen delivery to tissues, causing severe fatigue and breathlessness. Infection (high white cells) also causes tiredness. |
| Full Iron Studies | Serum Iron, Ferritin, Transferrin and Transferrin Saturation – a fuller picture than Ferritin alone | Low iron causes fatigue even without anaemia, and is one of the most missed causes of persistent tiredness. Ferritin alone can also look falsely reassuring if inflammation is present, which is why the full panel is used here. |
| Complete Thyroid panel with Free T3 and Antibodies | TSH, Free Thyroxine, Free T3, Thyroid Peroxidase Antibodies and Thyroglobulin Antibodies | Hypothyroidism (underactive thyroid) causes severe fatigue, brain fog, weight gain and cold intolerance. Checking the Antibodies as well as TSH picks up thyroid disease years before TSH alone would flag it. |
| Vitamin B12 | B12 levels in blood | B12 deficiency causes fatigue, brain fog, numbness and weakness. Vegans, vegetarians, and people with certain digestive conditions are at higher risk. Supplementation quickly restores energy. |
| Folate | Folate levels (Vitamin B9) | Folate deficiency contributes to anaemia and fatigue, and is often tested alongside B12. |
| Vitamin D | 25-OH Vitamin D | Low vitamin D causes fatigue, muscle weakness, low mood and poor immune function. In the UK, especially in winter, vitamin D deficiency is extremely common and easily fixed with supplementation. |
| HbA1c | Average blood glucose over about three months | Undiagnosed diabetes or pre-diabetes causes fatigue, poor concentration and unexplained weight changes. Early detection prevents serious complications and restores energy. |
| Insulin & C-peptide | How much insulin your body is producing, and how hard it is working to keep blood sugar normal | Insulin resistance can cause fatigue years before blood sugar itself becomes abnormal on HbA1c. Fasting is required for this component – see the note below. |
| Magnesium | Magnesium level in blood | Low magnesium is linked to fatigue, muscle cramps and poor sleep quality, and is easily corrected once identified. |
| Kidney Function | Urea, Creatinine and electrolytes | Reduced kidney function can cause fatigue and malaise, often with no other symptoms in the early stages. |
| Calcium | Calcium level in blood | Both high and low Calcium can cause fatigue, low mood and muscle weakness. |
| High-Sensitivity CRP | A sensitive marker of inflammation | Ongoing low-grade inflammation causes fatigue and malaise. CRP reveals whether inflammation is contributing, even when nothing else on the panel is abnormal. |
Who should get this test?
If you’re experiencing persistent tiredness despite what should be adequate sleep, this test is for you. It’s especially important if you’ve been told “nothing is wrong” or “it’s just stress” but you know something isn’t right.
- Persistent unexplained fatigue
- Brain fog or poor concentration
- Not refreshed after sleep
- Difficulty exercising
- Low mood
- Muscle weakness or cramps
- Numbness or tingling
- Previous “normal” GP tests
- Unexplained weight changes
- Multiple symptoms of unclear cause
What your results mean
Understanding your results
This panel often reveals a cause of fatigue that explains everything. Sometimes there’s one clear culprit – low ferritin, low B12, vitamin D deficiency – and supplementation transforms your energy. Sometimes multiple issues are found – perhaps low iron and low thyroid together, or vitamin D deficiency plus early insulin resistance. Our clinician reviews all 13 components together to build a complete picture of why you’re fatigued.
If anaemia is found, we investigate the cause (iron deficiency, B12 deficiency, folate deficiency) and treat it. If thyroid function is suboptimal, we discuss whether medication or lifestyle changes are appropriate. If B12 is low, we determine whether you need oral supplements, injections or dietary changes. If vitamin D or magnesium is deficient (both very common), supplementation usually brings a noticeable improvement within weeks. If Insulin or HbA1c suggest early insulin resistance or diabetes, we discuss prevention or management. If kidney function or Calcium is abnormal, we investigate further. The goal is finding exactly what’s causing your fatigue and fixing it.
What happens at your appointment
When you arrive at our Estover clinic in Plymouth, our clinician will spend time understanding your fatigue – how long it’s been going on, what makes it better or worse, how it’s affecting your life, what sleep is like, diet, stress, and any other symptoms. This context is crucial for interpreting results. The blood draw takes blood for all the tests in the panel – usually less than five minutes from a vein in your arm.
Your results are typically ready the next working day and are usually very interesting – many people are surprised to discover what’s been causing their tiredness. You’ll receive your results either at a follow-up appointment where our clinician explains what’s been found and exactly how to fix it (whether that’s iron supplementation, thyroid medication, B12 injections, vitamin D tablets or lifestyle changes), or online if you prefer. Either way, you get a complete explanation and a clear action plan. Most people find that once the underlying cause is treated, their energy returns and life improves dramatically.
Frequently asked questions
What’s the most common cause of fatigue you find?
Low iron and vitamin D deficiency are extremely common, especially in women and people who spend limited time in sunlight. Low thyroid is also very common but often missed because GPs typically only check TSH. Many people have more than one issue at once – low iron plus low vitamin D plus suboptimal thyroid. That’s why comprehensive testing finds causes that individual tests miss.
How quickly will I feel better after treatment?
It varies by cause. Vitamin D, magnesium and B12 supplementation often improve energy within 1-2 weeks. Iron takes longer – typically 6-8 weeks to feel significantly better and months to fully restore energy. Thyroid medication takes weeks to take effect and often requires dose adjustment. The important point is that once you start treating the cause, improvement is usually noticeable within weeks.
What if the panel finds nothing abnormal?
Normal results are reassuring – your fatigue isn’t due to the common medical causes tested. In that case, we discuss other possibilities such as sleep quality, stress management, low mood, chronic viral infections, or conditions requiring specialist investigation. Normal test results actually help narrow down what’s happening and guide further investigation if needed.
Do I need to fast before this test?
Yes. This panel includes Insulin, which requires a fasting sample. Have nothing to eat or drink except water for 10-12 hours before your appointment, and avoid heavy exercise for 48 hours beforehand, as this can affect the inflammation marker.
Is this the same as my GP would test?
Often not. Many GPs test only an FBC and thyroid TSH. This panel adds full Iron Studies, Thyroid Antibodies, B12, Folate, Vitamin D, HbA1c, Insulin, C-peptide, Magnesium, Kidney Function, Calcium and CRP – the markers that most commonly explain fatigue but that GPs often don’t test. It’s a much more comprehensive investigation designed specifically to find fatigue causes.
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Book your fatigue blood test in Plymouth
No referral needed. Results the next working day. All-inclusive for £164.
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