Feeling tired is one of those things that’s easy to put down to lifestyle. Work, stress, not enough sleep, too much screen time. But when the tiredness doesn’t lift after a decent night’s rest, when it’s there in the morning before the day has even started, when it’s affecting your concentration and your mood and your ability to get through the week, it’s worth asking whether something else is going on.
A targeted blood test can rule out, or identify, a number of common and very treatable causes of persistent fatigue. Here’s what’s worth checking and why.
Why Fatigue Is So Commonly Missed
Tiredness is vague. It’s not like a broken arm where something is visibly wrong. It’s easy for it to be attributed to stress, poor sleep habits, or just the demands of modern life, and in many cases those things are genuinely contributing. But fatigue is also one of the most common presenting symptoms of a range of conditions, many of which show up clearly in blood results and are straightforward to treat once identified.
The problem is that without testing, you’re guessing. And if the underlying cause is something like iron deficiency, hypothyroidism, or vitamin B12 deficiency, lifestyle changes alone won’t fix it. You need to know what you’re dealing with.
The Most Common Blood-Testable Causes of Fatigue
Iron deficiency and anaemia
Iron is essential for producing haemoglobin, the protein in red blood cells that carries oxygen around the body. When iron levels are low, your cells get less oxygen, and the result is fatigue, breathlessness, difficulty concentrating, and sometimes heart palpitations. Iron deficiency is particularly common in women of reproductive age but affects men too.
A full blood count will flag anaemia, but ferritin (stored iron) is the more sensitive marker. It’s possible to have low ferritin and normal haemoglobin, meaning you’re heading towards deficiency before it shows up in a standard blood count. Checking both matters.
Thyroid dysfunction
The thyroid gland regulates your metabolism. When it’s underactive (hypothyroidism), everything slows down. Fatigue, weight gain, feeling cold all the time, dry skin, brain fog, and low mood are all classic symptoms. Hypothyroidism is very common, particularly in women, and it’s easy to miss because the symptoms develop gradually and are easily attributed to other causes.
TSH (thyroid stimulating hormone) is the standard screening test. If TSH is raised, the thyroid is working harder than it should be, a sign it’s struggling to keep up. Free T4 gives a more complete picture of thyroid output.
Vitamin B12 deficiency
B12 is needed for nerve function and red blood cell production. Deficiency develops slowly and can cause profound fatigue, pins and needles, poor memory, low mood, and in more advanced cases, nerve damage. It’s more common in people who follow a plant-based diet, older adults, and people with certain gut conditions that affect absorption.
B12 deficiency is treatable, either through dietary changes, oral supplements, or injections depending on the cause and severity. But it needs to be identified first.
Vitamin D deficiency
Vitamin D deficiency is extremely common in the UK, where sunlight exposure is limited for much of the year. Low vitamin D is associated with fatigue, low mood, bone and muscle pain, and a higher susceptibility to infections. Many people are deficient without knowing it, particularly through winter and spring.
Supplementation is cheap and effective. But because high-dose supplementation can cause problems if levels are already adequate, it’s better to test first rather than guess.
Blood glucose and diabetes
Fatigue is one of the early symptoms of type 2 diabetes, which often develops without obvious warning signs. HbA1c gives a picture of average blood sugar over the past three months and is a reliable way to screen for pre-diabetes and diabetes. Catching it early makes a significant difference to long-term outcomes.
Kidney and liver function
Impaired kidney or liver function can cause fatigue as waste products that should be filtered out build up in the bloodstream. These conditions often have no obvious symptoms in the early stages, which is exactly why checking them is worthwhile even if you feel generally well apart from tiredness.
Hormonal causes
In women, hormonal fluctuations related to perimenopause and menopause are a very common cause of fatigue, often alongside poor sleep, low mood, and brain fog. Testosterone deficiency in men can cause similar symptoms. A hormone panel can identify whether levels are within the expected range for your age.
What Does the TATT Panel Include?
Our TATT (Tired All The Time) panel is designed to investigate the most common blood-testable causes of persistent fatigue in a single, cost-effective test. It includes:
- Full blood count (checking for anaemia)
- Ferritin (stored iron)
- Thyroid function (TSH and free T4)
- Vitamin B12 and folate
- Vitamin D
- HbA1c (blood glucose average)
- Kidney function
- Liver function
- Inflammatory markers (CRP)
Results are back the next working day. If anything is outside the normal range, we contact you directly and talk through what it means and what the appropriate next steps are.
Do I Need a GP Referral to Get These Tests?
No. You can book a TATT panel at Tamar Health directly, without seeing your GP first. If your results identify something that needs treatment or further investigation, we can advise on next steps, including follow-up consultations, prescribing, or referral.
Can I Just Ask My NHS GP to Test These Things?
In theory, yes. In practice, NHS GPs can only request tests they have specific clinical reason to order, and getting an appointment to make that request can take weeks. Some markers, like vitamin D, are not routinely tested on the NHS unless there’s a specific clinical indication. A private panel lets you check everything at once, on your timeline.
Frequently Asked Questions
Do I need to fast before the TATT panel?
Fasting isn’t essential for all markers in the panel, but for the most accurate blood glucose and cholesterol results we recommend fasting for 10 to 12 hours beforehand. A morning appointment works well as you can fast overnight.
How long will it take to get results?
Most results are back the next working day. We’ll contact you when they’re ready and discuss any findings that need attention.
What if everything comes back normal?
Normal results are genuinely useful. They rule out a range of common causes and point the investigation elsewhere, towards sleep, stress, mental health, or other factors. If results are normal and fatigue persists, a consultation with one of our clinicians is a good next step to explore other causes.
Can I add extra tests to the TATT panel?
Yes. If you want to add specific markers, for example a full hormone panel or PSA, just let us know when booking and we’ll include them.
Book a TATT Blood Panel in Plymouth
Investigate the most common causes of persistent fatigue with a single test. Results next working day. No referral needed.
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