Which blood values reveal what is behind fatigue?
For persistent fatigue, doctors usually look at the same set of markers: iron status (ferritin first), vitamin B12 and folate, vitamin D, thyroid function (TSH, free T4), blood sugar (HbA1c, glucose) and inflammation (CRP). Each of these can cause fatigue on its own, sometimes it is a combination.
The Iron & fatigue test measures iron status in full, from ferritin to transferrin saturation, plus B12, folate and CRP: 14 values for €99. Want to rule out thyroid, vitamin D and blood sugar as well, then the comprehensive test (52 values) is the broader test, and the includes it every year.
One measurement, broad picture
Instead of chasing tests symptomatically, you get the full picture. The app shows where you stand against the lab's reference ranges per value, which combinations are typical with fatigue and where the most likely starting points are.
Example: low ferritin with normal Hb points to iron deficiency that can play out for years before it leads to anaemia. High TSH with low T4 points to hypothyroidism. Both are classic fatigue causes that can be missed on a narrow test.
What do you do with the results?
Per marker, the app gives context: the lab's reference range, where you stand and what that means. For mild deviations, lifestyle adjustments can shift the trend.
For significantly off values, especially in combinations that may point to a condition, we recommend talking to your doctor. Optimize does not diagnose or treat.
Understand where your fatigue is coming from. Order the Iron & fatigue test, or pick the if you want thyroid, vitamin D and blood sugar measured every year too.
Test your iron levelsThe biomarkers that matter for fatigue
The areas where the cause of persistent fatigue is most often found. The first two are in the iron and fatigue test, the others in the comprehensive test and in the :
Beyond the comprehensive test, targeted add-ons let you go deeper into a specific marker or system.
Clarity on where your energy is leaking
How to investigate fatigue via your blood
Order the Iron & fatigue test
Thyroid, vitamin D and blood sugar too?
Book your draw in the app
See where the cause is
Re-test on target
Frequently asked questions
The key questions on blood testing for fatigue.
Ferritin (your iron store), iron, transferrin and saturation, the red blood picture, vitamin B12, folate and the inflammation marker CRP: those 14 are in the Iron & fatigue test. Vitamin D, thyroid (TSH, free T4) and blood sugar (HbA1c, glucose) are in the comprehensive test and in the .
Read first
Want to know which cause fits your symptoms first? These pages explain, per cause, what you measure and what you do about it.
Starts with empty stores, years before anaemia: ferritin, and what restless legs have to do with it.
When hemoglobin drops: how the red blood picture shows whether iron, B12 or folate is the cause.
Tired, cold and heavier for no reason: what TSH and free T4 say, and when it really is the thyroid.
Tingling, focus and fatigue: why a low B12 only becomes a deficiency with MMA.
Take control now.
Iron & fatigue
One draw at a location near you, results explained in the app.
- 14 blood values in one draw
- Results within 24 hours, in plain language
- No referral, no waiting list
- 250+ draw locations in the Netherlands
- Your trends on every retest, in the app
No referral needed · Results within 24 hours
Rather measure continuously? Core membership (€1 a day)