Yes, you do need to fast for 8 hours before the blood draw.
Fasting means, no food in any form. You are fine to drink clear liquids without sugar or fat.
The Golden Rule
If you are unsure if you can have something, the answer is NO. Standard fasting usually lasts 8 hours before your appointment.
Do
DO drink plain water. Hydration is highly encouraged. Being well-hydrated keeps your veins plump and makes the blood draw significantly easier and less painful. Tea and coffee without any additives are also fine.
DO take your prescribed medications. Unless your doctor specifically told you to skip a dose, take your daily medications with water as usual.
DO get a good night's sleep. Stress and lack of sleep can temporarily affect blood pressure and certain chemical levels.
DO keep warm. Wear a warm coat or layers. Warmth increases blood flow, making it easier for the phlebotomist to find a vein.
DO bring a snack for afterward. Bring a granola bar, fruit, or juice to consume immediately after the blood draw to prevent lightheadedness.
Don't
DON'T eat anything. This includes small snacks, mints, or a single bite of toast. Food triggers digestion, which changes your blood sugar, enzymes, and lipid (fat) levels.
DON'T chew gum (even sugar-free). Chewing stimulates your stomach to produce digestive juices, which can alter test results. It may also affect insulin levels even if there is no sugar.
DON'T drink alcohol for 24 hours prior. Alcohol can affect liver enzymes and blood sugar for longer than 12 hours. It also causes dehydration.
DON'T smoke. Smoking affects blood pressure and white blood cell counts. Try to abstain for the entire fasting period if possible.
DON'T exercise heavily 48h before the test. Strenuous workouts before a test can elevate certain enzymes (like CPK/creatine kinase) and skew results. Keep physical activity light. You are totally fine to cycle or jog to the appointment itself.