Brain Iron, Not Blood Iron
Dopamine synthesis depends on iron. In restless legs the deficit is frequently in brain iron even when blood counts are normal, which is why ferritin is the meaningful marker and haemoglobin is not.
Many clinicians target a ferritin above 75 to 100 ng/mL in restless legs specifically — considerably higher than the threshold used for general iron deficiency.
What Makes It Worse
Several common medications aggravate it: most antihistamines, many antidepressants, antinausea drugs and some antipsychotics all reduce dopamine signalling.
Alcohol, late caffeine, nicotine and sleep deprivation do the same by a different route. A medication review is often the single highest-yield step.
Augmentation
Dopamine agonists work well initially and then, in a substantial proportion of people, cause augmentation: symptoms start earlier in the day, spread to the arms and become more intense than before treatment.
This is why current guidance has moved toward correcting iron first and using alpha-2-delta agents rather than reaching for dopamine agonists early.
