Why do you have to fast before blood taking?

It is the morning of your health screening that you have signed up for. You have been given a reminder to fast at least 8 hours prior to the blood taking. But your stomach is growling and without caffeine, you are feeling very cranky and irritable early in the morning. A thought comes to your mind: Perhaps consuming a slice of bread and a nice little cup of espresso will not cause much difference to the health screening results.


Unfortunately, even if you take only a piece of biscuit or a sip of tea, it will still affect your results. In fact, you are also supposed to fast from smoking, stop taking your regular vitamins and even exercise 8 hours prior to the health screening. These can rev up your digestion and the results will not be accurate. However, if you have prescription medications, do take them regardless of the fasting, unless your doctor has cleared you to skip it. This is especially so for participants diagnosed with high blood pressure and/or diabetics. Be reminded to inform the health screening staff that you have taken these medications so that they are aware should there be any anomaly in the results.

Not all blood test requires fasting. Below is a list of tests that you will strictly need to fast:

  1. Blood glucose test
  2. Cholesterol test
  3. High density lipoprotein test (HDL)
  4. Low density lipoprotein test (LDL)
  5. Triglyceride level test
  6. Gamma-glutamyl transferase (GGT)

Drinking water, from the tap or the bottle is completely fine. However, carbonated water, or a squeeze of lemon is off-limits. Having water during fasting actually helps your veins to become plumper and more visible, allowing the phlebotomists to locate the point of entry for the needle easily.

What if you forget and slip up? Do inform the health screening staff so that the results can be interpreted accurately. For the blood tests that require fasting, it is recommended to reschedule it as the results will be skewed and there is no point in getting pricked by the needle.


Not to worry, the moment you finish taking your blood, your fast is over. You may want to bring a snack or a drink to consume the moment you finish the health screening.

For more information on health screening and blood taking, you may contact Integrated Wellness Pte Ltd at 6250 7623 or send an email to appointments@iwell.sg. Our friendly nurses and staff will be glad to assist you in your queries.