This page is a tool to get a sense of what happens when you take regular doses of a medication. The basic idea is that the body metabolizes your medication at a steady rate, characterized by the halftime. You can usually find this rate on e.g. the Wikipedia page for your medicine. You enter your dosage, how often you take it (in terms of the delay between dosage, common values are every 24h, every 12h or every 8h), and the amount of time you want to see graphed.
Once you have the graph, you can hover over it with the mouse to get values at different times, and you can read off some descriptive statistics at the bottom: the average amount over a few days at the end, the standard deviation and the range of these amounts.
While a mathematician I am NOT a trained medical professional. This page and this tool should NOT be taken as authorative, or as any sort of advice for your own medication. Always consult with your doctor before any changes to your medication routines.