Does Drinking Coffee Kick You Out of Ketosis?

January 2, 2026 •

3 min read

According to a 2017 study published in the Canadian Journal of Physiology and Pharmacology, caffeine significantly increases ketone production in healthy adults. This suggests that, far from kicking you out of ketosis, drinking black coffee can actually support it. However, the impact of coffee on ketosis depends heavily on what you add to it.

Quick Summary

Black coffee does not break ketosis and may even boost ketone production, but adding sugar, milk, or other high-carb ingredients can immediately disrupt the ketogenic state. The key is to consume coffee correctly with keto-friendly additions like MCT oil or heavy cream.

Key Points

Plain black coffee is keto-friendly: With zero carbs and calories, unsweetened coffee does not interfere with ketosis.
Caffeine can boost ketone production: Studies show that caffeine can increase the body's ketone levels and enhance fat oxidation.
Additives are the main threat: Sugar, milk, and most flavored creamers contain high levels of carbs and sugar that will knock you out of ketosis.
Opt for keto-friendly mixers: Heavy cream, MCT oil, and zero-carb sweeteners like stevia or monk fruit are excellent choices.
Consider Bulletproof Coffee: Blending coffee with healthy fats like grass-fed butter and MCT oil can provide a sustained energy boost.
Listen to your body's sensitivity: Pay attention to how caffeine and coffee on an empty stomach affect you, and adjust your intake accordingly.

Understanding Ketosis and Coffee

Ketosis is a metabolic state where your body burns fat for energy, producing molecules called ketones, instead of relying on glucose from carbohydrates. Maintaining this state requires consuming a very low-carb, high-fat diet. For coffee lovers, the question of whether their daily brew interferes with this process is crucial.

The Impact of Plain Black Coffee

Unsweetened, black coffee is essentially a zero-calorie, zero-carbohydrate beverage, making it perfectly safe for a ketogenic diet. The primary active ingredient, caffeine, has been shown to be beneficial for those in ketosis.

Enhanced Ketone Production: Research indicates that caffeine can stimulate the body's production of ketones. In one study, participants who consumed caffeine saw a significant dose-dependent increase in plasma ketones.
Increased Fat Oxidation: Caffeine is known to increase lipolysis, the breakdown of fat into fatty acids. These fatty acids are then available to the liver to be converted into ketones.
Boosted Metabolism: Caffeine can increase your resting metabolic rate, helping to burn more calories and supporting weight loss goals often associated with the keto diet.

The Additive Dilemma: How Your Coffee Stops Ketosis

While the coffee itself is keto-friendly, the real danger lies in the additions. Many popular coffee extras are loaded with sugars and carbohydrates that can immediately halt ketosis.


Ingredient	Keto Impact	Carbs/Serving (Approximate)	Insulin Response
Sugar/Syrups	Breaks ketosis	5-20g+ per tbsp	High
Cow's Milk (2%)	Breaks ketosis	~12g per cup	High
Conventional Creamer	Breaks ketosis	Varies, can be high	High
MCT Oil/Coconut Oil	Maintains/Boosts ketosis	0g	Very Low
Heavy Cream	Keto-friendly in moderation	~0.5-1g per tbsp	Low
Unsweetened Plant Milk	Keto-friendly	Varies, typically low	Low
Stevia/Monk Fruit	Keto-friendly	0g	None (generally)

How to Enjoy Keto-Friendly Coffee

Enjoying coffee on a keto diet simply requires some adjustments to your routine. The goal is to focus on adding healthy fats and avoiding carbohydrates.

Bulletproof Coffee: This popular option combines coffee with grass-fed butter or ghee and MCT oil. Blending it creates a creamy, frothy drink rich in healthy fats that can promote satiety and energy without impacting ketosis.
Heavy Cream: A small splash of heavy cream adds richness without the high carb count of traditional milk. It's a great choice for those who don't enjoy black coffee.
Sugar-Free Sweeteners: Use natural, zero-carb sweeteners like stevia or monk fruit to satisfy your sweet tooth without the blood sugar spike. Be aware that some artificial sweeteners might still impact certain individuals.
Spices: Add flavor with zero-carb spices like cinnamon, nutmeg, or pumpkin spice. These can offer a depth of flavor without breaking ketosis.

Potential Downsides and Considerations

While coffee is generally safe for ketosis, there are some factors to keep in mind.

Caffeine Sensitivity: Some people are more sensitive to caffeine and may experience anxiety, jitters, or insomnia. Excessive caffeine can also raise cortisol levels, a stress hormone, which can potentially hinder ketosis in some individuals.
Digestive Issues: Drinking coffee on an empty stomach, which is common during intermittent fasting on keto, can cause digestive upset or acid reflux for some. If this happens, try a lower-acidity cold brew.
Hydration: Coffee has a diuretic effect. It's important to stay well-hydrated with water and replenish electrolytes, especially during the initial phases of a keto diet.

Conclusion: Coffee is Fine, But Choose Your Additions Wisely

Drinking plain black coffee does not kick you out of ketosis and may even help you along. The key is to be mindful of the ingredients you add. By avoiding sugar, conventional milk, and sugary syrups, and instead opting for keto-friendly additions like heavy cream, MCT oil, or zero-carb sweeteners, you can continue to enjoy your daily cup while staying in a ketogenic state. As with any dietary change, listen to your body and adjust your intake and preparation methods as needed to feel your best. You can learn more about how different beverages affect ketosis and other fasting goals from sites like Zero Longevity Science.

Frequently Asked Questions

Regular cow's milk contains lactose, a natural sugar that can disrupt ketosis and cause an insulin spike. It is best to avoid it. Instead, opt for unsweetened plant-based milks like almond or coconut milk, or use a small amount of heavy cream.

Yes, sugary coffee drinks, such as lattes with added syrups, will almost certainly break ketosis. They are full of sugar and carbohydrates, which will spike your blood sugar and halt the ketogenic process.

Bulletproof Coffee, made with coffee, MCT oil, and grass-fed butter, is a popular keto-friendly option. It provides healthy fats for energy and satiety, but it does contain calories, so it's not considered a true fast.

Zero-calorie sweeteners like stevia and monk fruit generally do not affect blood sugar and are considered keto-friendly. However, some artificial sweeteners can still impact gut health and trigger an insulin response in sensitive individuals, so it's best to monitor your personal reaction.

Yes, decaf coffee is completely fine on a keto diet. It contains virtually no calories or carbs and provides many of the antioxidants of regular coffee without the stimulating effects of caffeine, making it a good choice for later in the day.

Most experts recommend a moderate intake of 1-3 cups per day, or up to 400 mg of caffeine. High doses can lead to negative side effects like anxiety and sleep disruption, which can indirectly hinder your diet.

Black coffee can be consumed during intermittent fasting on a keto diet, as it won't break the fast and can enhance fat-burning effects. However, if your goal is gut rest or maximizing autophagy, some purists recommend only water.