Does vaping break a fast?

The answer depends on the type of fast

Different kinds of fasting have different rules and goals. The answer to whether vaping breaks them changes accordingly.

Vaping and intermittent fasting

If you are doing 16:8 or similar for weight loss or metabolic health, vaping sits in a grey area. The strictest definition of fasting is zero calorie intake. By that standard, vape juice contains trace amounts of PG and VG that are technically calories, but in such tiny quantities (typically under 5 calories a day across normal use) that they do not meaningfully affect ketosis or fat burning.

The calorie content of normal vaping over a fasting window is so low that it almost certainly does not break a calorie-based fast in any practical sense. Whether nicotine should still be considered fast-breaking is more debatable.

What nicotine does that might matter for fasting outcomes:

• Mild insulin response. Some research suggests nicotine briefly raises insulin slightly, though the effect is small and short-lived.
• Appetite suppression. Nicotine reduces hunger. This actually helps most people get through fasting windows.
• Metabolic stimulation. Nicotine raises metabolic rate by 7 to 15%. Useful if your goal is fat loss, less aligned with deep restorative fasting goals.
• Blood sugar fluctuations. Particularly in people with diabetes, nicotine can affect glucose regulation in ways that matter more than the calorie content.

Vaping and religious fasting

For Muslims observing Ramadan, the consensus among scholars is that vaping breaks the fast. The reasoning follows the same logic that has been applied to smoking for decades: anything intentionally inhaled into the body during fasting hours is considered fast-breaking, regardless of calorie content.

The argument is not about calories. It is about deliberate intake of a substance through the mouth. That makes vaping equivalent to smoking in this context, even though the chemistry is different.

For most Christian, Jewish and Hindu fasting practices, the rules vary by denomination and tradition. Anyone fasting for religious reasons should ask their religious authority directly. General internet guidance is not a substitute for your faith leader's ruling.

Vaping before blood tests and surgery

When a doctor tells you to fast before a procedure, vaping is almost always included in that instruction. Two specific concerns:

1. Blood tests for glucose, cholesterol or cardiovascular markers

   Nicotine can affect blood glucose, insulin and inflammatory markers. Vaping before the test may give inaccurate readings, which leads to wrong conclusions.

2. Pre-surgery fasting

   The NHS includes vaping in “stop before your op” advice. Nicotine narrows blood vessels and affects healing and anaesthesia. Generally stop at least 24 hours before, ideally 4 weeks for planned surgery.

3. Pre-anaesthetic fasting

   The fasting itself (typically 6 hours without food or drink) sometimes covers nicotine. Ask the team specifically. If unsure, do not vape on the morning of any procedure.

If you want to vape while fasting

For intermittent fasting where you have decided vaping is acceptable, a few things make it work better.

• Use zero-sugar e-liquids. All TPD-compliant UK e-liquids are essentially sugar-free, but flavoured varieties have more sweetening. Plain or unsweetened blends are cleanest.
• Stay well hydrated. Both fasting and vaping are mildly dehydrating. Water is essential during any fasting window.
• Consider lower nicotine. Reduces the appetite-stimulating dopamine spikes and insulin response. Closer to the metabolic state fasting aims for.
• Listen to your body. If vaping during a fasting window makes you hungrier rather than less hungry, that is a sign nicotine is affecting your blood sugar.

The bottom line