The blood sample for a blood test must be taken on an empty stomach, as the results can be falsified depending on what you eat or drink beforehand. After ingestion, the body processes the components of the food consumed, which circulate through the bloodstream.

A blood test for sugar levels does not provide reliable results because the blood sugar level after eating varies from the fasting state. Fasting before a blood test provides a reliable diagnosis of bodily functions.

So how long before the blood test should you stay sober?

Blood values that can be distorted by food intake are usually blood sugar, blood fat, cholesterol, triglyceride and metabolism. Doctors therefore recommend a certain fasting period before the blood sample is taken, usually between 8 and 12 hours. The blood sample is usually taken early in the morning, so that the last time is in the evening before going to bed. Before a blood glucose test, you should fast for at least 8 hours before the blood sample is taken. For cholesterol tests, fasting is even more important to get an accurate result, so fasting for 12 hours before the blood sample is taken is recommended.

During fasting before a blood test, you should only drink water. Medication prescribed by the doctor can be taken, with the exception of oestrogen, corticosteroids, androgens, oral contraceptives, certain diuretics, antibiotics, anti-psychotics and niacin.
Water is the only liquid that is allowed, do not drink sweetened drinks under any circumstances. Smoking and physical activity or chewing gum should be avoided. It goes without saying that alcohol should not be consumed.

As several values are usually tested at the same time during a blood test, some of which require 8 hours of fasting, others 12 and others none at all, you should fast for 12 hours before the blood sample is taken to ensure the most accurate results.