Eating before a fasting blood test changes the result, and the test has to be repeated. Here is how to prepare before you come to our Valenzuela branches.
In short
- Fasting blood sugar always needs fasting, and a lipid profile usually does.
- Fast for 8 to 12 hours. Plain water is fine.
- Take your regular medicine unless your doctor says otherwise, and ask the front desk what your request needs.
Which tests need fasting
- Fasting blood sugar (FBS). Always.
- Lipid profile (cholesterol and triglycerides). Usually.
- Some other chemistry tests, depending on what your doctor ordered with them.
A CBC, urinalysis, fecalysis and most other tests do not need fasting. If you are not sure, read us your request over the phone and we will tell you.
How long to fast
Fast for 8 to 12 hours. The easiest way is to finish dinner by 8 PM, skip the midnight snack, and have your blood drawn first thing in the morning.
What you can and cannot have
- Plain water: yes. It makes the blood draw easier.
- Coffee, tea, juice, milk, soft drinks: no. Even black coffee can affect results.
- Candy and chewing gum: no.
- Alcohol: avoid it for 24 hours before the test.
- Cigarettes: avoid them on the morning of the test.
What about my medicine?
Take your regular medicine unless your doctor tells you otherwise. If you take medicine for diabetes, ask your doctor whether to take it before or after the blood draw, and tell our staff what you have taken.
If you ate by mistake
Tell us before the blood draw. It is better to reschedule than to get a result that misleads your doctor.
On the day
- Come early. Mornings are easiest for fasting tests.
- Bring your doctor’s request, a valid ID and your HMO card (health insurance card) if you use one.
- Bring a snack to eat right after.
To understand the two most common fasting tests, read fasting blood sugar vs HbA1c. See all our laboratory tests, or the fasting tests included in our check-ups.
Tests mentioned in this article
This article is general information and does not replace advice from your own doctor.
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Call before you come, or just walk in
Our front desk can tell you if your test needs fasting, which doctor is in today, and what your HMO covers.