You can almost always have plain water when you’re fasting for blood work, and it’s actually recommended rather than forbidden.

Quick Scoop

Fasting for blood work usually means: no food, no drinks except plain water for 8–12 hours before the test.

Can you have water?

  • Yes, you can drink plain still water while fasting for blood tests.
  • Water does not affect common fasting tests like glucose or cholesterol, so it’s considered safe.
  • Being hydrated can make veins easier to find and the blood draw smoother.

What kind of water is okay?

Stick to:

  • Plain, unflavored still water.
  • Small, regular sips are fine; you don’t need to chug, just avoid getting dehydrated.

Avoid:

  • Flavored water (even “zero sugar”).
  • Sparkling water if it’s flavored or sweetened; some guidance allows plain sparkling, but many clinics say still only, so when in doubt, choose still.
  • Anything with lemon or lime slices, sweeteners, or additives.

What drinks are NOT allowed?

While fasting, typically you should not have:

  • Coffee (even black) or tea
  • Juice or smoothies
  • Milk or creamers
  • Soda or energy drinks
  • Alcohol
  • Broth or “liquid meals”

These can stimulate digestion or change sugar and fat levels, and that can skew your results.

Other fasting tips (quick list)

  • Usual fasting window: 8–12 hours before the test, depending on the labs ordered (your doctor or lab slip should specify).
  • Avoid chewing gum, mints, or candy during the fast—even sugar-free ones—unless your provider says otherwise.
  • Ask your doctor what to do with morning medications; some should be delayed, others taken with a sip of water.

One important caveat

Different labs or doctors sometimes give very strict, test-specific instructions. If what they wrote on your form or text message conflicts with anything above, follow their instructions and call to confirm —they know exactly which tests they’re running.

TL;DR: For “fasting blood work,” you can almost always drink plain water, and it’s encouraged, but no other drinks or additives—when in doubt, call the lab or your doctor to double-check.

Information gathered from public forums or data available on the internet and portrayed here.