Dr.CardioMD said:
The objection nobody has made: this only works if the measurement is doing what we assume it is doing, and that assumption has not been tested here.
Adding the part of the answer the thread has not reached. Order of operations matters more than any single choice here: establish a baseline, change one thing, wait long enough for it to express itself, then measure again under the same conditions.
Worth separating that from injection-site reactions, which this thread keeps folding into the same question. They behave differently and the advice does not transfer.
That is the short version; the long version is somebody else's post.