Final answer:
A lipid panel should be drawn when a patient is fasting in a tube. This test measures the levels of total cholesterol, LDLs, HDLs, and triglycerides in the blood.
Step-by-step explanation:
A lipid panel should be drawn when a patient is fasting in a tube. Blood samples are collected into tubes containing lithium heparin and centrifuged to obtain plasma. The lipid panel test measures the levels of total cholesterol, LDLs, HDLs, and triglycerides in the blood to assess the risk of a heart attack.