Persistent fatigue is frustrating because it is both common and non-specific. “I am tired all the time” can describe poor sleep, emotional exhaustion, low exercise tolerance, daytime sleepiness, weakness or a combination of several things.
There is no single fatigue blood test
A useful assessment starts with context. How long has the fatigue been present? Is sleep restorative? Has weight changed? Are periods heavy? Is there breathlessness, pain, low mood, anxiety, fever, bowel change or a new medication?
Common contributors a GP may consider
Possibilities can include poor sleep, chronic stress, burnout, depression, anxiety, iron deficiency, anaemia, thyroid dysfunction, diabetes, infection, medication effects, nutritional issues and other chronic medical conditions.
When do blood tests help?
Targeted tests can be useful when the history suggests a reasonable question to answer. A blood count may help investigate anaemia, iron studies may be relevant where iron deficiency is suspected, and thyroid or glucose testing may be appropriate in the right context.
What if all the tests are normal?
Normal tests do not mean the fatigue is imaginary. Sleep, mental health, work demands, chronic stress, physical deconditioning and other factors may still need attention. The next step is to use the results to narrow the picture rather than simply ordering a larger panel.
Persistent fatigue deserves assessment when it is new, worsening, unexplained or clearly affecting normal functioning.