If you have been asked to fast before a blood test, it is because food and drink can change some results. Fasting helps give a clean, reliable reading.
What does fasting mean?
It means no food and no drinks other than plain water for a set number of hours before your sample is taken. For most tests this is 8 to 12 hours, often overnight.
Which tests usually need fasting?
- Fasting blood sugar
- Lipid profile (cholesterol and triglycerides)
- Some liver and iron tests
Many other tests, such as a complete blood count, thyroid tests or HbA1c, usually do not need fasting. The instructions for your specific test will tell you.
Tips for a smooth fasting test
- Drink plain water. Staying hydrated makes the blood draw easier.
- Book an early morning slot, so you do not wait long without eating.
- Avoid tea, coffee with milk or sugar, juice, chewing gum and sweets during the fast.
- Take your regular medicines unless your doctor has told you otherwise. Ask if you are unsure.
- Eat normally after the sample is taken.
If you forgot or ate by mistake
Tell the person collecting your sample. They may advise you to rebook, so that your result is accurate.
This article is general information and not medical advice. Please talk to your doctor about your own results and health.
