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Yes, during intermittent fasting you can sip zero-calorie items; any snack with calories ends the fast window.

No, smoking during fasting for a glucose test isn’t allowed; nicotine and smoke can alter blood sugar readings.

No, using cannabis while fasting for a lab blood test can skew results; stick to water only unless your clinician says otherwise.

Yes—and no: smoke has no calories, but many fasting rules still treat inhaled substances as breaking the fast.

No, cannabis before a fasting blood test can skew results; skip it for the full fasting window your clinician sets.

Yes, you can train during a 72-hour fast, but keep sessions light, drink enough fluids, and stop if dizziness, chest pain, or weakness shows up.

No, a week-long fast isn’t safe for most people; medical oversight and clear criteria are needed.

No, avoid vaping before a fasting blood test; nicotine and aerosols can skew results, so stick to water unless your clinician says otherwise.

No, vaping breaks religious fasts; for calorie-control fasts, plain vapor without nicotine or sweeteners usually adds no calories.

Yes, visiting the dentist while fasting is fine for routine care; if sedation is planned, follow pre-procedure fasting rules from your care team.