What code would I use for encounter for venipuncture for routine metabolic analysis. The closest I can come up with is Z51.81-Encounter for therapeutic drug level monitoring; but in this case we are not monitoring drug levels- what do I use??
I wouldn't code anything for the venipuncture.
If patient has hyponatremia (currently taking Na tabs), or low Mag levels (taking MgOX supplements), etc. you could code that deficiency, because patient is currently receiving treatment to correct the condition, agency is monitoring progress, and it puts patient at risk of re-hospitalization. If it is something that was resolved, and patient not taking meds to currently correct the imbalance, but the MD just wants it 'checked up on', I wouldn't code anything at all for it.