2 ms·Testing the actual intervention seems arguably more useful than testing blood concentrations.by colechristensen 4y agoTesting the actual intervention seems arguably more useful than testing blood concentrations.nradov 4y agoYou're missing the point. The amount of the intervention should vary. There is a huge variation in response to varying levels of variation. This is just common knowledge in medicine.nradov 4y agoSorry I meant varying levels of supplementation (too late to edit).