If you are tired all the time and do not know why, a small group of blood tests can check several common medical causes: anaemia and iron deficiency, thyroid problems, B12 or folate deficiency and diabetes. Blood tests cannot explain every case of tiredness – poor sleep, stress and lifestyle cause a great deal of it – but they can help identify or make several common medical causes less likely and guide what to look at next. Vitamin D status can also be relevant for some people, although national guidance does not recommend routine testing for everyone with unexplained tiredness. Most routine results are back within around 24 hours.
First, be honest about the usual causes
Most tiredness is not a medical mystery. The NHS lists the common causes as not getting enough sleep, an unhealthy lifestyle, stress, depression and life challenges, hormonal changes such as pregnancy or the menopause, illnesses like glandular fever and COVID-19, and some medicines. If any of those fit, a blood test is unlikely to be the first answer.
NHS advice is to see a GP if you have been feeling tired for a few weeks and you are not sure why, if tiredness affects your daily life, or if you have other symptoms such as weight loss or mood changes. A private blood test can sit alongside that advice: it can check the common medical causes quickly, but it is not a substitute for assessment of persistent or concerning symptoms.
The blood tests that look for the common causes of tiredness
These are the tests most often used to investigate ongoing tiredness, with Mango Medical’s published prices:
| Test | What it looks for | Price |
|---|---|---|
| Full blood count (FBC) | Anaemia and the different cells in your blood. The NHS says iron deficiency is the most common type of anaemia, and an FBC is the usual first test. | £36 |
| Iron / ferritin | Ferritin measures the iron stored in your body. Iron deficiency is the most common type of anaemia. | £54 |
| Thyroid function | Thyroid-stimulating hormone (TSH) and thyroxine (T4), the hormones checked when an underactive thyroid is suspected. | £60 |
| B12 and folate | Vitamin B12 or folate deficiency anaemia, which the NHS says is important to diagnose and treat as soon as possible. | £58 |
| Vitamin D | Vitamin D status, tested where clinically appropriate – NICE does not recommend routine testing unless someone has symptoms of deficiency, is at particularly high risk, or there is another clinical reason. | £50 |
| HbA1c / diabetes test | Your average blood glucose over approximately the previous 2-3 months – the test used to diagnose type 2 diabetes and prediabetes. | £37 |
Prices from the current Mango Medical Price List. The published test price covers clinic blood collection and laboratory processing. If you already know which test you need, and that test is clinically appropriate, no £45 consultation fee is routinely added.
Match your symptoms to the most likely test
Your symptoms can point towards one cause, which makes a single test the cheapest way to an answer:
| If you notice | The NHS says this can suggest | The test that checks it |
|---|---|---|
| Lack of energy, paler than usual skin, shortness of breath or noticeable heartbeats | Iron deficiency anaemia | Full blood count and ferritin |
| Feeling extremely tired with weight gain that is hard to explain | An underactive thyroid | Thyroid function (TSH and T4) |
| Extreme tiredness, sometimes with pins and needles or a sore tongue | Vitamin B12 or folate deficiency | B12 and folate |
| Feeling very tired, very thirsty, and peeing more often than usual, particularly at night | Type 2 diabetes | HbA1c / diabetes test |
| Risk factors for vitamin D deficiency, such as very limited sunlight exposure | Low vitamin D | Vitamin D test, where clinically appropriate |
Symptoms overlap, and the NHS cautions against self-diagnosis. If several rows sound like you, that is a reason to ask a clinician which tests are appropriate rather than to book all of them.
One combination needs prompt attention: if you are very thirsty, passing urine much more frequently than usual, losing weight unexpectedly or becoming increasingly unwell, seek medical assessment rather than relying solely on a private blood test. The NHS page on type 2 diabetes symptoms explains why.
A single test or the tiredness profile?
If your symptoms point clearly at one cause, a single test is the cheapest answer – a full blood count is £36. If several causes are on your list, individual tests add up quickly.
Mango also lists a Tired all the time / anaemia profile at £140. It includes a full blood count, ESR, iron/TIBC, ferritin, active B12 and red-cell folate, so it looks mainly at anaemia, iron status, B12/folate and inflammation. It does not include thyroid function, vitamin D or HbA1c, so if those are on your list they are booked separately. The value is straightforward: a full blood count, iron/ferritin and B12/folate bought individually would already cost £148 at the published prices, while the £140 profile covers those areas plus ESR.
If you are unsure what you need, the £45 Initial Health Consultation adds a discussion of your symptoms, a 10-point health assessment and a recommendation about which tests are appropriate. That can be cheaper than guessing – and it avoids paying for tests you do not need.
What the results will and will not tell you
Most routine blood test results are usually back within around 24 hours, although turnaround varies by test and some specialist tests take longer. Confirm the expected turnaround for your test when you book.
A laboratory report and a clinical explanation are different things. The NHS says blood test results can be complicated and you should ask a healthcare professional if you do not understand them. A separate £45 follow-up consultation is available if you want a detailed discussion of your results and next steps. If a result is clinically concerning or needs prompt action, Mango will contact and advise you appropriately – you will not be asked to pay for a consultation simply to be told something needs medical attention.
Some causes of tiredness do not show up on blood tests. Sleep apnoea, ME/CFS, stress and depression are diagnosed in other ways, so a normal set of results does not mean nothing is wrong. A normal set of results can make some common medical causes less likely and help guide what to consider next.
When to see your GP instead
See a GP if you have felt tired for a few weeks and do not know why, if tiredness affects your daily life, or if you also have other symptoms such as weight loss or mood changes – or if someone has told you that you make gasping, snorting or choking noises in your sleep, which can suggest sleep apnoea.
If your GP or another clinician has already requested a blood test, Mango can undertake GP-requested tests where appropriate. Explain the request when you enquire so the request and reporting arrangements can be clarified before you book. Results can be shared with your usual clinician where appropriate and with your agreement.
To talk through which test fits your symptoms, call Mango Medical.
Clinic appointments in Bristol, with home and workplace blood collection across Bristol and South Gloucestershire by arrangement at additional cost.
Frequently asked questions
Can a blood test tell me why I am always tired?
It can check several common medical causes – anaemia and iron deficiency, thyroid problems, B12 or folate deficiency and diabetes. It cannot rule out every cause: poor sleep, stress, depression, sleep apnoea and ME/CFS do not show up on these tests. A normal result can still be useful because it helps narrow down what to consider next.
What is the first blood test to ask for when tired all the time?
There is not one first blood test that is right for everyone. A full blood count is commonly used to look for anaemia, while symptoms and medical history may point towards thyroid function, diabetes, B12/folate or other investigations. If you are unsure, ask a clinician rather than guessing.
Do I need to fast before a tiredness blood test?
Most tests used to investigate tiredness need no special preparation – the NHS notes you do not need to do anything to prepare for a full blood count. Some tests do require fasting, so confirm the preparation for your specific test when you book.
How long do the results take?
Most routine blood test results are usually back within around 24 hours, although turnaround varies depending on the individual test and some specialist tests take longer. Ask for the expected turnaround when you book.
Will my GP see my private blood test results?
Only with your agreement. Results can be shared with your usual clinician where appropriate, and if your GP requested the test, the reporting arrangements are clarified before booking.
This guide is general information, not a diagnosis or personalised medical advice.