letter no. 1
How long do I actually need to fast, and can I drink coffee?
the desk replies — Lipid profile and fasting glucose need 8–12 hours with water only — no coffee, tea or juice, since caffeine and calories both shift the values. CBC, HbA1c, vitamin D and thyroid tests do not require fasting at all. If your panel mixes both types, fast for the whole thing and eat straight after the draw.