While there are specific tests that require a person to fast, most tests that you will do don’t require fasting. In fact, only a few tests require fasting really. Because eating will affect certain tests results your doctor will ask you to fast.
However, most tests do not require fasting. When you need to fast for a test your doctor or lab will inform you. Follow their instructions.
What Types of Blood Tests Require Fasting?
Glucose and Lipid tests are the most common blood tests that require fasting. You will need to fast 8 to 12 hours before the tests. You can only drink water. No juice, coffee, gum, soda or other beverages.
Lipid Tests: cholesterol, HDL, LDL, triglycerides
Glucose Tests: Fasting Blood Sugar (FBS), Oral Glucose Tolerance Test (OGTT)
And that is basically it. Other tests that require fasting are few. Your doctor will inform you beforehand which tests to fast for.
Fasting Blood Sugar (FBS) and Lipid are part of a few panels. So, if you are doing a Basic Metabolic Panel (BMP), Comprehensive Metabolic Panel (CMP) or a General Health Panel you will need to fast beforehand.
What is the Difference Between a Fasting and a Non-Fasting Blood Test?
Fasting blood tests are certain tests that require a person to fast from midnight or for 8 to 12 hours before the tests are done. During that time the person can only drink water. Non-fasting blood tests are those tests that can be done at any time without the need to fast.
Almost every time fasting blood tests are done in early morning. It can be done later in the day as long as the person has been fasting. Non-fasting blood tests are done any time.
Which Blood Tests Do Not Require Fasting?
Some of the most common non-fasting blood tests include kidney function, liver function, pre-natal, thyroid function and STI screen. It should be okay if you eat for these tests unless your doctor tells you not to.
Below are tables listing some of the most common non-fasting blood tests that your lab or doctor may ask you to do.
| Panel/Profile | Tests |
| Renal Function (RFT) | Bun, Creatinine, Electrolytes |
| Pre-Natal | CBC, Group & RH, Sickle Screen, HIV, Syphilis, OCP |
| Cardiac | CK-MB, Troponin |
| Thyroid Function (TFT) | T3, T4, TSH |
| Acute Hepatitis | Hepatitis A Antibody (IgM), Hepatitis B Surface Antigen, Hepatitis B Core Antibody (IgM), Hepatitis C Antibody |
| Liver Function (LFT) | Total Protein, Albumin, Total Bilirubin, AST, ALT, ALP, GGT |
| Arthritis | Rheumatoid Factor (RH), CCP Antibody (IgG) |
| STD Screen | Syphilis, HIV, Gonorrhea, Chlamydia, HSV (1&2/IgM+IgG) |
Over 71 Tests That Do Not Require Fasting
| Chemistry Tests |
| Glucose (RBS) O’Sullivan (OST) Bun Creatinine Electrolytes Uric Acid AST (GOT) ALT (GPT) ALK. PHOS Amylase CK (CPK) CKMB LDH Total Protein Albumin Calcium Phosphorus Bilirubin (Total & Direct) Lithium HBA1C Magnesium Myoglobin Iron Iron/TIBC GGT 24HR Urine Creatinine Troponin 1 BNP |
| Hematology Tests |
| CBC Retics Sickle Screen ESR PT/INR PTT Fibrinogen D-Dimer Group & RH Hb Electrophoresis Indirect Coombs |
| Hormone Tests |
| Cortisol Insulin DHEA Estrogens Estradiol/Estriol LH FSH Prolactin Testosterone (F) Testosterone (M) T3, T4, TSH HCG Progesterone |
| Immunology Tests |
| Rheumatoid Factor (RF) ASTO SLE H. Pylori AB Dengue Screen HBsAg Screen HCV HAV IgM Rubella Toxo IgG & IgM Leptospira Ab Monospot Varicella IgG MMRV CMV IgG & IgM CRP |
| Cancer Markers Tests |
| CA 27.29 CA 19.9 CA 15.3 AFP CEA CA 125 PSA |
Note: Instructions may vary from one lab to another and from one doctor to another for any particular test. Follow instructions of the respective lab or doctor.