Practical guide
Fasting for a blood test
For some blood values it is important that you fast, for others it is not. Below you read what fasting means exactly and when it is needed.
What does fasting mean exactly?
Fasting usually means not eating or drinking for 8 hours before the sample, except water. Black coffee, unsweetened tea and chewing gum can already affect some values; if in doubt, leave them out. Take your medication as usual, unless stated otherwise.
For which blood values is it needed?
Fasting mainly matters for glucose (blood sugar) and a full lipid panel (cholesterol, triglycerides). For many other tests, such as thyroid, vitamins and iron, fasting is usually not required. Because a draw often combines several values, we then advise fasting to be safe.
Relevant blood values
Frequently asked questions
How long should I fast?
Usually 8 hours. Drinking water is allowed and even recommended, it makes the draw easier.
Can I drink coffee?
Preferably not. Black coffee can affect some values; stick to water if you need to fast.
Should I skip my medication?
No, take your medication as usual, unless your doctor or the test instructions say otherwise.
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