Why fasting matters before a blood sugar test

By LabNest Team · 02 Jul 2026

Fasting before certain blood tests helps your lab measure a true baseline. For a fasting blood sugar test, most labs recommend 8 to 12 hours without food. Water is fine and usually encouraged. Avoid tea, coffee, juice, and chewing gum during the fasting window, since even small amounts of sugar can shift the result. Book an early-morning home collection slot so your fasting window fits neatly into your sleep. If you take regular medication, ask your doctor whether to take it before or after the sample. On collection day, stay hydrated and relaxed — being calm helps the phlebotomist find a vein quickly and makes the whole process painless.