Medically reviewed by Jenneh Rishe, RN —

Written by Tim Jewell and Alina Sharon — Updated on February 1, 2024

Blood tests can be used to help a doctor identify a variety of health conditions, including infections, anemia, high cholesterol, vitamin deficiencies, organ failure, HIV, cancer, diabetes, and more. Doctors use blood tests to analyze the behavior of substances like proteins, cells, or chemicals in your blood.

This can give them a picture of your overall health and help them diagnose different diseases, monitor chronic conditions, assess your organ function, and determine your immune system strength.

Regular blood testing is one of the most important ways to keep track of your overall physical well-being. We’ve partnered with Lifeforce to bring you this overview article on blood tests.

What do blood tests check for?

Blood tests can help your doctor determine how different organs in your body are working. Examples of organs whose malfunctions can be visible in a blood test include your heart, thyroid, liver, or kidneys.

Your doctor can also use blood tests to search for markers of diseases and health conditions such as:

Diabetes, HIV, Anaemia, Cancer, Coronary Heart disease. Even if a person does not have heart disease, a blood test can show whether they may be at risk of developing the condition.

Other blood tests can indicate whether the medications you’re taking are working properly or assess how well your blood is clotting.

When do you need a blood test?

You would typically undergo a blood test in the following cases:

During your annual physical exam:

Your doctor may order a general blood test such as the complete blood count (CBC).

You’re at risk of a health condition: You may need to undergo a specific blood test if you have a higher chance of developing a specific disease or condition or if you have a known genetic mutation that can cause a condition.

You have a known condition: Sometimes,you already have a diagnosis, but your doctor needs to know how your condition is progressing or to evaluate your treatment.

You’re having symptoms: If you are experiencing symptoms, your doctor may need to run a blood test to confirm a suspected diagnosis or to see if you need more specialized testing.

You’re pregnant: During pregnancy, your doctor will do a CBC and test your blood type.

Before surgery: You may need to do a blood test if your surgeon wants to check for anything that might put you more at risk during the procedure, such as excessive bleeding, for example.

You want to optimize your health: Knowing the levels of various blood components, such as HDL and LDL cholesterol, can allow you to tweak your diet or fitness plan to maximize healthy habits.