Blood tests are not currently able to detect lung cancer. However, a doctor may need to conduct blood tests after diagnosis. They may run blood chemistry tests to take a look at a person's organ function. This can help them determine whether the cancer is affecting other parts of the body, which could mean that it has spread. They may also order a complete blood count test. This test can detect abnormalities in different blood cell types. This could warn the doctor of potential issues with bleeding or infections during lung cancer treatment.