You're sleeping — or trying to — eating reasonably, not obviously overworked, and yet you're exhausted by mid-afternoon most days, some weeks worse than others. It's one of the most common reasons people see a GP, and one of the most frustrating to have dismissed with ‘it's probably just stress’. Persistent, unexplained fatigue very often has a real, identifiable, treatable cause — and the only way to know is to test for it. The Tired All The Time (TATT) panel checks 44 markers across the eight areas of health most likely to explain ongoing tiredness, in a single blood draw.
The most common causes of persistent tiredness
When patients come to us with ongoing, unexplained fatigue, a handful of causes come up again and again — most of them straightforward to test for and treat:
- An underactive thyroid — one of the most common and most treatable causes of fatigue, often alongside weight gain, low mood and dry skin.
- Iron deficiency — can cause tiredness and breathlessness well before it progresses to anaemia, and is easily missed on a basic blood count alone.
- Low vitamin B12 or folate — both linked to fatigue and low mood, and easily corrected once identified.
- Vitamin D deficiency — extremely common in the UK, and associated with tiredness and aching muscles.
- Raised blood sugar — undiagnosed diabetes or pre-diabetes frequently presents first as unexplained fatigue.
- Underlying inflammation or post-viral fatigue — picked up by CRP, and worth ruling out if tiredness followed an infection or illness.
When to seek help
Most causes of persistent tiredness are common and manageable once identified — this is a screening test, not an emergency assessment. Seek prompt or urgent assessment instead if fatigue is severe, rapidly worsening, or comes with unexplained weight loss, breathlessness, chest pain or other new symptoms.
As a rule, seek urgent care for severe, sudden or rapidly worsening symptoms, and book a routine test for milder, longer-standing concerns like the ones above.
What the Tired All The Time (TATT) checks
Rather than testing one thing at a time, the Tired All The Time (TATT) panel screens 44 markers across 9 areas of your health in a single blood draw. Here's what each group can tell you:
Thyroid
This panel checks TSH, free T4, free T3 and thyroid antibodies. An underactive or overactive thyroid can cause tiredness, weight changes, low mood, hair thinning or a fast or irregular heartbeat — often mistaken for stress or "just getting older" — so a clinician can spot dysfunction even before it's obvious from symptoms alone.
Iron status
This panel checks ferritin, serum iron, TIBC, transferrin and transferrin saturation. Low iron is one of the most common, treatable causes of fatigue, breathlessness and poor concentration, often well before a full anaemia develops — a complete iron picture is far more useful than a ferritin test alone.
Vitamins
This panel checks vitamin D, vitamin B12, folate and magnesium. Deficiencies here are widespread in the UK and are linked to fatigue, low mood, muscle aches and poor immunity — and are simple to correct once identified.
Full blood count
This panel includes a full blood count — red cells, white cells, platelets and related indices — one of the single most useful all-round checks available, screening for anaemia, infection and abnormalities in your blood.
Blood sugar
This panel checks glucose, HbA1c and insulin, screening for diabetes and pre-diabetes, which can develop silently for years with no obvious symptoms.
Inflammation
This panel checks C-reactive protein (CRP), a general marker of inflammation in the body that can point towards infection, a chronic inflammatory condition, or increased cardiovascular risk.
Kidney function & salts
This panel checks creatinine, eGFR, cystatin C, sodium, potassium and urea. Kidney function can decline silently for years before it's noticed, so these markers give an early warning of reduced kidney function, dehydration or salt imbalances.
Liver function
This panel checks albumin and alkaline phosphatase. Liver enzymes can flag early strain from alcohol, medication, weight gain or fatty liver disease long before any symptoms appear.
Bone & mineral health
This panel checks calcium and phosphate, giving an early picture of bone and mineral health that can also flag problems affecting energy and muscle function.
Tired All The Time (TATT) — £217
CQC-regulated · Rated 4.88/5 on Doctify · Open 7 days 8am–8pm · No referral needed
Why the Tired All The Time (TATT) is the right test
The reason a single test rarely answers “why am I so tired?” is that the common causes overlap and mimic each other — low iron and an underactive thyroid can look almost identical from the outside, and a normal-range result on one test means little without the others for context. The TATT panel was built specifically around this problem: instead of testing thyroid, then iron, then vitamins separately over several appointments, it covers all eight likely areas — thyroid, iron, B12 and folate, full blood count, blood sugar, vitamin D, inflammation, and kidney/liver/salts — in one visit.
A clinician reviews every result, explains what's driving your tiredness (or rules out the common causes if everything comes back normal), and recommends sensible next steps.
Frequently Asked Questions
Why am I tired all the time?
Persistent tiredness has many possible causes. Some of the most common and treatable are biochemical — an underactive thyroid, low iron, low vitamin B12 or folate, low vitamin D, raised blood sugar, or underlying inflammation. This 44-marker panel checks for all of these in one blood draw, so a clinician can help identify or rule out the common causes and explain what your results mean.
What if my results all come back normal?
That’s still useful information — it helps rule out the common biochemical causes of fatigue, so your clinician can focus on other explanations such as sleep quality, stress, medication side effects or, less commonly, a condition needing further specialist investigation.
Do I need to fast before this blood test?
Yes — because this panel includes glucose and HbA1c, we recommend avoiding food for around 8-10 hours beforehand (water is fine). Our team will confirm exact preparation when you book.
Do I need a GP referral to book this test?
No referral is needed. You can book directly online or by calling 0121 387 3727. Same-week appointments are available 7 days a week, 8am to 8pm.
Can I claim this on private health insurance?
Self-funded blood tests are usually paid for directly rather than through insurance, as most insurers require a referral first. If you would like to use insurance, call us on 0121 387 3727 and our team will advise on the best route for your policy.
Reference ranges vary between laboratories and are influenced by age, sex and other individual factors. This article is for general information only and does not replace a clinical consultation — every result in the Tired All The Time (TATT) panel is reviewed by a clinician before it's released to you. Further reading: Lab Tests Online UK →