If you have seen your NHS GP about chronic fatigue and been told your blood tests are normal, there is a good chance the right tests were not run. Standard NHS blood panels for fatigue are often limited to a full blood count and sometimes a thyroid check. That misses several common and entirely treatable causes of persistent exhaustion. This article explains what a thorough fatigue blood panel should include, what each test looks for and why it matters.
Full Blood Count (FBC)
The starting point. Checks for anaemia, which reduces the oxygen your blood delivers to tissues and organs. Anaemia causes fatigue, breathlessness and poor concentration. It can be caused by iron deficiency, B12 deficiency, folate deficiency or chronic disease. The FBC identifies anaemia but does not always identify the cause, which is why further tests are needed.
Ferritin and Iron Studies
Ferritin measures your iron stores. This is the test the NHS most commonly omits. Iron deficiency produces severe fatigue, hair loss and poor concentration long before anaemia appears on the FBC. A ferritin below 30 micrograms per litre indicates depleted stores even when the haemoglobin is technically normal. Many people with ferritin in this range are told their blood tests are fine, because the FBC alone looks acceptable.
Thyroid Function (TSH and Free T4)
Underactive thyroid (hypothyroidism) is found in 1 in 20 people and produces fatigue, low mood, weight gain, brain fog and cold intolerance. TSH is the most sensitive marker. A raised TSH indicates the thyroid is struggling even before hormone levels drop significantly. This should always be included in a fatigue workup.
Vitamin D
Vitamin D deficiency is extremely common in the UK and is a well-established cause of fatigue and low mood. Most people in London are deficient for much of the year. It is cheap to test and cheap to treat, yet it is frequently not checked in standard NHS fatigue panels.
Vitamin B12 and Folate
B12 deficiency causes fatigue, brain fog, mood disturbance and neurological symptoms. It is common in vegetarians, vegans, people on long-term metformin or proton pump inhibitors, and older adults. Folate deficiency produces similar symptoms and often accompanies B12 deficiency.
HbA1c (Diabetes Screening)
Undiagnosed type 2 diabetes is a significant cause of persistent fatigue that is easy to miss because it develops gradually. HbA1c measures average blood glucose over the preceding three months. Pre-diabetes, which is even more common, also causes fatigue and is reversible with lifestyle changes if caught early.
Hormones
In men, low testosterone produces fatigue, low mood, poor concentration and reduced motivation that is almost indistinguishable from burnout. In women, perimenopause is one of the most commonly missed diagnoses in the fatigue workup. FSH and oestradiol, combined with a careful history, identify it. Both conditions are treatable and respond quickly when the diagnosis is made.
Morning Cortisol
True adrenal insufficiency is rare, but it produces profound fatigue and should be excluded in anyone with severe, unexplained exhaustion who has not responded to other treatment. Morning cortisol is the screening test. It is not routinely included but is worth considering when other tests are normal and fatigue is severe.
Getting the Right Tests in London
At AristoGP, Dr Schoinas arranges the full panel described above in a single blood draw at the clinic. Results are reviewed with you personally within 24 to 72 hours. If something is found, treatment starts immediately. If everything is genuinely normal, you know that, and the conversation moves to other causes. GP consultation from 100 pounds. Phlebotomy 39 pounds. Same-day appointments at 1-5 Portpool Lane EC1N, four minutes from Chancery Lane.