Chronic Fatigue Blood Test
Apr 4, 2026
Chronic Fatigue Blood Test
A chronic fatigue blood test investigates the treatable medical conditions that cause persistent exhaustion—including thyroid dysfunction, iron deficiency (even without anaemia), vitamin D and B12 deficiency, diabetes, kidney and liver problems, and hormonal imbalances—because fatigue is a symptom, not a diagnosis, and identifying the cause is the first step to feeling better. Up to 40% of people presenting with fatigue have an identifiable medical cause.
At Blood Test London, our comprehensive fatigue panel costs from £345 with results in 2-3 days. A doctor always reviews every result, looking for patterns across all markers.
Medical Causes of Chronic Fatigue
Common Treatable Causes
Cause | Prevalence in Fatigue | Blood Test Detects? |
|---|---|---|
Iron deficiency | 20-30% | ✓ Yes (ferritin) |
Thyroid dysfunction | 10-15% | ✓ Yes |
Vitamin D deficiency | 15-20% | ✓ Yes |
Vitamin B12 deficiency | 5-10% | ✓ Yes |
Diabetes/prediabetes | 5-10% | ✓ Yes (HbA1c) |
Anaemia | 10-15% | ✓ Yes (FBC) |
Kidney/liver problems | 3-5% | ✓ Yes |
Hormonal imbalance | Variable | ✓ Yes |
Chronic infection | Variable | Partially |
Key insight: Many people are told fatigue is "just stress" without proper testing. We find treatable causes frequently.
What Our Fatigue Panel Includes
Thyroid Function (Key Priority)
TSH, Free T4, Free T3
Thyroid antibodies
Both underactive AND overactive thyroid cause fatigue
Iron & Blood Health
Ferritin (most important—often low before anaemia)
Full iron studies
Full blood count
Vitamin B12 and folate
Metabolic Health
HbA1c (diabetes/prediabetes)
Fasting glucose
Liver function
Kidney function
Vitamins & Minerals
Vitamin D (deficiency epidemic in UK)
Magnesium
Inflammation
CRP (chronic inflammation causes fatigue)
Hormones (If Indicated)
Cortisol
Testosterone (men and women)
Why Standard NHS Testing Often Misses Causes
NHS Approach | Our Approach |
|---|---|
Basic thyroid (TSH only) | Full thyroid panel including T3 |
Ferritin "normal" at 15 | Optimal ferritin >70 for energy |
No vitamin D unless requested | Always included |
No B12 unless anaemic | Always included |
Results within normal range = fine | Optimal ranges for function |
"Normal" isn't always optimal. A ferritin of 20 is technically normal but can cause significant fatigue.
Common Findings We Identify
Suboptimal Iron (Most Common)
Ferritin 15-30: "Normal" but symptomatic
Particularly common in women with periods
Responds to supplementation
Thyroid Issues
Underactive thyroid (hypothyroidism)
Sometimes "subclinical" but still causing symptoms
Hashimoto's thyroiditis (autoimmune)
Vitamin Deficiencies
Vitamin D deficiency (extremely common in UK)
B12 deficiency (especially vegetarians, elderly, on metformin)
Metabolic Problems
Prediabetes (HbA1c 42-47)
Early diabetes
Blood sugar instability
Multiple Deficiencies
Often several issues combine
Addressing all needed for recovery
Our Fatigue Testing Options
Essential Fatigue Panel - £345
Thyroid function
Iron studies + ferritin
Full blood count
Vitamin D, B12, folate
HbA1c
Liver and kidney function
CRP
Doctor review
Comprehensive Fatigue Investigation - £445
All above plus:
Full thyroid panel with antibodies
Magnesium
Cortisol (morning)
Detailed consultation
Complete Fatigue + Hormone Assessment - £545
Full fatigue panel
Full hormone profile
Extended consultation
Follow-up plan
What If Blood Tests Are Normal?
If comprehensive testing is normal, consider:
Chronic Fatigue Syndrome (ME/CFS): Diagnosis of exclusion
Sleep disorders: Sleep apnoea, insomnia
Mental health: Depression, anxiety
Lifestyle factors: Sleep, stress, overwork
Post-viral fatigue: After COVID, EBV, etc.
Our doctor can guide next steps if tests are normal.
Book Your Fatigue Panel
Price: From £345
Results: 2-3 days
Doctor review: A doctor always reviews every result
Fasting: Preferred (10-12 hours for glucose accuracy)
Best time: Morning for hormone accuracy
Book via WhatsApp | Phone: 020 3951 3429
FAQ
My GP says my tests are normal but I'm still exhausted—should I retest?
Yes. We use optimal ranges, not just "normal." Many people with symptoms have suboptimal levels that are technically in range.
How quickly can I feel better if a cause is found?
Depends on the cause. Iron: weeks to months. Thyroid: weeks on medication. B12: often rapid improvement with treatment.
Could it be multiple things?
Yes—we often find several suboptimal markers. Addressing all of them is key to recovery.
Blood Test London by The Wellness. Fatigue testing from £345. A doctor always reviews every result.