Can I drink water before fasting blood work?
Last updated September 3, 2026.
Yes - plain water is the explicit exception, and it helps: hydrated veins draw easier. MedlinePlus defines the fast as nothing to eat or drink except plain water, with coffee, tea, juice, gum, smoking, and exercise all ruled out. Medications usually continue with a sip of water - confirm yours when the test is ordered. If you accidentally break the fast, tell the lab; some results can be interpreted around it.
What to do
- Drink water normally. It is allowed and makes the draw easier.
- Keep it plain. No lemon, sweeteners, or flavor drops - additives count as breaking the fast.
- Skip everything else. Coffee, tea, juice, gum, smoking, and exercise all move the numbers.
- Confess accidents. The lab can often still use the draw if they know what you had.
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