Do you need to fast before having a venous blood draw?
Feb 07, 2023
Source: Cainiu Health
Dr. Zhang Jianbin
Introduction
In most cases, venous blood sampling requires fasting, although specific requirements depend on the type of blood test being performed and whether eating would affect the laboratory results. Blood is generally drawn from a vein before various medical tests. For tests such as liver function, blood glucose, blood lipids, rheumatism panel (three items), kidney function, and electrolyte levels, blood must be drawn while the patient is in a fasting state.
In most cases, venous blood collection requires fasting, although specific requirements depend on the type of blood test being performed and whether eating would affect the laboratory results. It is recommended to consult a healthcare professional before blood collection to avoid inaccurate test results.
Blood samples are generally drawn from veins prior to various medical tests. For tests such as liver function, blood glucose, lipid profile, rheumatism panel (rheumatoid factor, anti-CCP, etc.), kidney function, and electrolyte levels, blood must be drawn while the patient is fasting. Additionally, patients should not eat or drink anything after midnight the night before the test. This is because food and drink can alter these laboratory values, leading to inaccurate results. However, for routine blood tests such as complete blood count (CBC), erythrocyte sedimentation rate (ESR), blood typing, anemia panel, and certain immune system tests, fasting is not required, as eating does not affect the outcomes.
Vein blood sampling helps assess a patient's health status and enables doctors to make accurate diagnoses and determine appropriate treatment plans, thereby promoting recovery. After venipuncture, the puncture site should be pressed firmly for 3–5 minutes to prevent bleeding.
