How much water should you drink before having blood drawn?
Ideally, start drinking more fluids the day before your blood draw, and continue to drink water before you have your blood drawn. Excessive amounts aren't necessary; most sources recommend that an adult drink 64 ounces of water per day for good health, which is more than adequate for having your blood drawn.
Diabetes is a condition that can lead to there being too much sugar in the blood. A fasting blood glucose test measures levels of sugar in the blood to see if they are healthy. It is important that a person has not had anything to eat or drink other than water for 8 to 10 hours before a fasting blood glucose test.
- Food does not usually affect your blood tests for hormonal studies, so it's okay to eat. However, you may be told to fast before having a prolactin blood test. Be sure to speak to your nurse if you are unsure about eating before these tests.
- Inform your doctor of any medications, herbs, or supplements that you regularly take. Do not eat or drink anything for 8 hours before a blood test for iron level, TIBC, or transferrin. No fasting is necessary before a test for ferritin levels. Do not take iron pills for 24 hours before the test.
- It depends on the type of blood test you're having. You can eat and drink as normal before some blood tests. But if you're having a "fasting blood test", you will be told not to eat or drink anything (other than water) beforehand. You may also be told not to smoke before your test.
Updated: 26th November 2019