Can You Drink Black Coffee When Fasting?

Do you have to fast for an upcoming doctor’s appointment? Can you drink black coffee when fasting? Learn more about this topic below!

Can You Drink Black Coffee When Fasting - black coffee and utensils at the top of a table mat
Black coffee can impact your blood sugar levels

Black coffee can impact your blood sugar levels.

Whether you have weight loss goals, are trying to follow a new diet, or have an upcoming wellness appointment, you may need to fast from time to time. If you are trying intermittent fasting, you may have questions about what you can and cannot drink.

For example, will a morning cup of coffee violate your fasted state? Is it going to kick you out of ketosis? How will this impact your blood pressure and blood glucose levels?

Before you reach for that cup of joe, understand how it might impact your intermittent fast. Whether you can drink one or two cups of coffee during your fasting period depends on why you are fasting. 

Take a look at some helpful information we have put together about black coffee and fasting!

Black Coffee And Fasting For Blood Tests

First, if you have a doctor’s appointment coming up, understand that even black coffee can impact your blood sugar levels. While the carb content of black coffee is negligible, and it is close to calorie-free, it still has caffeine in it. 

Coffee consumption can impact your heart rate and blood pressure, throwing off your vital signs when you arrive at the doctor’s office. 

Furthermore, coffee is a diuretic. This means that it can dehydrate you, which can impact a wide variety of blood test results. This includes your electrolyte levels, your triglyceride levels, and even your liver enzymes. 

There is a reason why doctors want you to have an empty stomach when you arrive at the office for a blood test. Even if you just drink regular coffee, your blood test results might be thrown off. 

So if you’re fasting because you need to have bloodwork done, you should avoid coffee, green tea, or black tea to get the most accurate results.

You might also be interested in our explainer on can you drink coffee with Vyvanse.

Bulletproof Coffee: Helpful For Ketosis

If you are a coffee drinker and you’re trying to follow the keto diet, there are certain types of coffee you should stay away from. 

For example, sweetened coffee drinks will quickly cause your body to stop producing ketonesCalorie-free sweeteners like stevia will not have this effect, but anything with real sugar will.

Without carbs, your body starts burning fat for energy instead. This process is called ketosis

If you supply your body with calories in the form of carbs, it will stop burning your fat cells, hurting your weight loss goals. If you are looking for coffee you can drink on the keto diet, then Bulletproof Coffee might be for you.

Bulletproof Coffee contains MCT oil in the form of coconut oil, which drives up its fat content. On a ketogenic diet, you will consume a lot of fat, encouraging your body to stay in ketosis. Even though Bulletproof Coffee can provide you with a lot of energy, it does contain calories (and a lot of them).

Therefore, this is a beverage that you should drink in moderation. One or two cups during your morning coffee break should be sufficient.

Can You Drink Coffee On An Intermittent Fast?

clock, knife and fork on a wooden board
Intermittent fasting with coffee may reduce inflammation throughout the body

Intermittent fasting with coffee may reduce inflammation throughout the body. The benefits of fasting can be combined with the antioxidants in black coffee to improve your health.

Drinking moderate amounts of zero-calorie or low-calorie beverages will not break your fast. This includes black coffee, black or green tea, and herbal teas as long as they aren’t sweetened. A single cup of espresso or black coffee only contains between two and three calories. Therefore, this should not ruin your fast. 

There are numerous benefits of intermittent fasting with coffee as well. For example, consuming coffee while fasting may reduce inflammation throughout the body. If you are someone who suffers from aches and pains, intermittent fasting could help you reduce inflammation, making you feel more comfortable.

It is also possible that drinking coffee regularly while fasting could reduce your risk of developing heart disease. There are a few drawbacks as well. For example, one study showed that drinking multiple cups of coffee in a day could increase insulin levels.

This suggests that multiple cups of coffee could reduce your insulin sensitivity, impacting your metabolic health. If you are trying intermittent fasting for the first time, you should monitor how it impacts your body.

Final Word on Can You Drink Black Coffee When Fasting

If you are fasting, you need to follow the guidelines carefully. In some cases, you may be able to drink coffee. In other cases, you might need to avoid it.

It depends on why you are fasting.

For example, if you are giving intermittent fasting a try, you may be able to drink black coffee. Because black coffee has a low number of calories, this should not break your fast. Lattes and cappuccinos should be avoided because milk contains protein, fat, and carbohydrates and will break your fast.

You should try not to add sweeteners to your coffee. This could break your fast. It will certainly break your state of ketosis if you are trying to follow the keto diet. 

Finally, if you have a doctor’s appointment coming up, your doctor may have asked you to fast because he needs to ensure the accuracy of your blood test results. Coffee contains caffeine and soluble plant matter, so it can throw off your blood work, impacting your doctor’s ability to make diagnoses like type 2 diabetes.

Follow the instructions of your doctor if you have been told to fast.

FAQs About When Fasting Can You Drink Black Coffee

Can I drink coffee on the keto diet? 

Black coffee is keto-friendly. On the keto diet, you need to limit your intake of carbohydratesBlack coffee does not contain a lot of carbohydrates

You can drink this on the keto diet. However, you cannot add any sugar or sweeteners to your coffee, this will knock your body out of ketosisArtificial sweeteners would be alright if they don’t contain any carbohydrates.

Can I drink coffee while fasting intermittently?

If you are in a fasting window on the intermittent fasting diet, you can still drink black coffeeBlack coffee only contains between 2 and 3 calories per cup. This shouldn’t break your fast or stop autophagy from happening.

Will drinking coffee impact my blood test results? 

There are certain blood tests that require you to fast before your blood is drawn. If your doctor has told you to fast, do not drink coffee. This can throw off the results of many common blood tests including a cholesterol panel, blood sugar levels, and renal function panels.


  • David R

    Job experience includes extensive work as a teaching assistant, tutor, and guest lecturer and extensive employment in the healthcare field. Have published multiple research papers and numerous poster presentations on various healthcare research topics.