@never2many My knowledge of 'therapeutic drug monitoring" (as a nurse) sounds like when we or (for) docs order say theophylline levels, or some psych drugs, some heart meds etc. To basically get an actual drug level in the blood to see if the drug is staying at the appropriate level for treatment. Depending of course what they are testing and what reason. I would think it would also have had what drug they are checking the level for? For example theophylline (or digoxin or dilantin) the ones I'm most familiar with.. the blood test is ordered say 12 hours after last dose, and if it is timed like this, you HAVE to do it at exact time, then they can see if they need to increase your dosage (it too low), stay the same-keep monitoring, or lower your dose (too high-and a lot of these drugs they do this on, get toxic in your system easily) so it's basically to stay safe and make sure you are maintaining the proper levels for the best therapeutic result. If you are on one of the drugs they do this for, they would have made you aware of the fact you have to get frequent blood tests for this reason, and you would know what that is. I hope this helps?? If you have any questions, let me know and I can try to help.