Here’s how I do it.   In this example I want to take 1.5mg but I only have a 2.5mg tablet.    I use a spreadsheet to do these maths.  Plenty of examples around the forum.   1.5/2.5 == 0.6, or 60% ( the amount of the tablet I want to ingest )   0.6 of 50 ml == 30 ml ( amount of liquid suspension to ingest )   50 - 30 == 20 ml ( amount of liquid suspension to discard )   - pour a glass (1) of filtered water - have an empty glass (2)