The blue line shows the concentration of a drug in the blood, at a given moment in time. The drug is taken once a day. It takes the body four days to completely absorb one dose of the drug.In 12 hours, concentration in the blood is halved. This is known as elimination half-life.

Pharmacokinetics is a branch of pharmacology which studies what the body does to a drug. Pharmacokinetics looks at how a substance enters, moves through and exits the body. It relates how the dose delivered affects the concentration within the body. It is closely related to another branch of pharmacology, pharmacodynamics, which describes how a drugs affects the body.