Can I Drink Water Before A Fasting Blood Test?


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Arianna Vaccaro Profile
Arianna Vaccaro answered
The short answer to your question is: Yes, you may drink water before a fasting blood test. Some sources say that any water should only be taken in small amounts whilst others say that you should drink only as much as you would normally in order to avoid changing your usual fluid balance.

A fasting blood test is normally done for blood  lipids - cholesterol, LDL (low density lipoproteins), HDL (high density lipoproteins) and triglycerides - or blood sugar levels. Both of these substances are easily affected by what you eat or drink, which is the main reason for the no eating rule.

Water will not affect the readings of blood lipids or sugars, and of course, you may need to take your usual medication as well with liquid. It is also important not to be dehydrated because your kidneys might otherwise be wrongly suspected of malfunctioning.

Most sources state that beverages such as tea, coffee and sodas are to be avoided, but one doctor claims that black coffee did not affect the outcome of results.

There seems to be some disagreement about how long the fasting period should be. One authority insists that the fast should start 12 to 16 hours before the blood test, but another is satisfied with nine to 12 hours, so it is probably best to consult with your own medical practitioner on their policy to be sure.

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