What happens to the carbon-14 levels in a living thing after it dies?

After a living organism dies, it no longer takes in carbon-14 from the atmosphere. As a result, the carbon-14 within its tissues begins to decay at a known rate, with a half-life of about 5,730 years. Over time, the levels of carbon-14 decrease, which can be measured to estimate the time since the organism's death, a method known as radiocarbon dating.