Short answer: Tap the round Dashboard button at the bottom of the screen and choose Levels. Pick a medication at the top. The ring shows an estimate of how much is in your system, worked out from the doses you logged and the medication's half-life. Below it are the Pharmacokinetics chart, your Consistency and a 7-day comparison.
Before you start: Every number on this page is an estimate the app calculates. It is not a blood test and can differ from what is really in your body.
Dose Track builds the curve from the amount and time of each dose you logged and the half-life stored for that medication. If you forget to log a dose, or log it at the wrong time, the estimate will be off too.
When a medication has no human data behind its half-life, the label reads Half-life (est.). For long-acting shots the ring can also say it includes what is still releasing from the injection site.
Levels only lists medications in your protocol. If you have no protocol, the page says No medications in your protocol. Custom medications are left off on purpose, because the app has no checked half-life data for them. Some blends have no chart either.
Read more about the ideas behind the chart: half-life, steady state and trough level.
See also: Half-life calculator · Glossary: steady state