Always tired? The blood tests worth doing first

Being tired all the time is one of the most common reasons people come to a GP, and one of the hardest to pin down. It can be sleep, stress, workload or mood - and often is. But a handful of common, treatable things also cause it, and they show up on ordinary blood tests.

This is a general guide to what usually gets checked first. It is not a substitute for being assessed, and which tests are right for you depends on your symptoms and history.

Full blood count

The first-line test. It looks at your red cells, white cells and platelets, and it is how anaemia is picked up. Anaemia is a genuinely common cause of persistent tiredness, particularly in women with heavy periods, and it is straightforward to treat once identified.

Iron studies

You can be low in iron before you are anaemic, and a full blood count alone can miss that. Ferritin reflects your iron stores, which is why it is often checked alongside.

Where blood tests confirm iron deficiency and oral iron is not suitable, tolerated or effective, an iron infusion may be considered - but that is a decision made after results and an assessment, not before.

Thyroid function

An underactive thyroid slows everything down and fatigue is usually the first thing people notice, often with weight change, feeling cold, or low mood. It is a simple test and easily treated.

Vitamin D

Deficiency is common in the UK generally and more so through winter. It is associated with tiredness and aching, and it is easily corrected.

Vitamin B12 and folate

Both are needed to make healthy red blood cells. Deficiency causes fatigue, and sometimes pins and needles or problems with memory and concentration. More likely if you eat little or no meat, or have a condition affecting absorption.

HbA1c

Checks your average blood sugar over the past two to three months. Undiagnosed diabetes can present as tiredness along with thirst and needing to pass urine more often.

What the results actually tell you

A normal set of results is genuinely useful information - it rules out a list of things and points the conversation elsewhere, usually towards sleep, mood, or something that needs a longer look.

The number on its own is rarely the whole answer, which is why our results are reviewed by a clinician and explained to you rather than emailed over as a table.

To talk through which tests make sense for you, ring 01482 766555.