What Happens if I Drink Coffee on an Empty Stomach in the Morning?

December 26, 2025 •

3 min read

A large percentage of coffee drinkers begin their day with a cup, often before eating. However, this morning habit can lead to side effects like heartburn, anxiety, or an upset stomach for some individuals.

Quick Summary

Drinking coffee before eating can increase stomach acid, cause blood sugar changes, and trigger cortisol spikes. However, it can also provide a faster energy boost, but effects vary based on individual tolerance.

Key Points

Digestive Irritation: Coffee stimulates stomach acid, which can cause heartburn, acid reflux, or upset stomachs when consumed without food.
Increased Anxiety and Jitters: Faster caffeine absorption on an empty stomach can intensify effects, leading to anxiety, jitteriness, or restlessness for sensitive individuals.
Hormonal Spikes: Drinking coffee first thing in the morning can increase cortisol levels, potentially adding to stress and impacting mood.
Blood Sugar Swings: Research suggests that coffee on an empty stomach can impair blood glucose control, causing energy spikes followed by crashes.
Individual Variation: The effects vary widely from person to person; for many healthy individuals, it causes no significant issues.
Simple Solutions: Eating a small snack, adding milk, or trying a darker or cold brew can mitigate negative digestive side effects.

The Science Behind Coffee on an Empty Stomach

Starting the day with coffee is a common practice. Yet, is it advisable to consume it without food? While generally safe for healthy adults, reactions can differ. Several physiological changes occur when caffeine and the acidic compounds in coffee interact with an empty digestive system. Understanding these mechanisms helps determine if this routine is suitable.

The Effect on Your Digestive System

Coffee's acidity can stimulate stomach acid production when consumed on an empty stomach. Without food as a buffer, excess acid may irritate the stomach lining. This can potentially cause heartburn, indigestion, and acid reflux. Caffeine can also relax the lower esophageal sphincter, increasing the likelihood of stomach acid rising. People with GERD or IBS may be more susceptible to these effects.

Hormonal and Neurological Impact

Caffeine absorbs faster on an empty stomach, potentially leading to anxiety or jitters. Coffee can also trigger cortisol release. Since cortisol levels naturally peak in the morning, coffee can cause an additional spike, which can affect mood and cause irritability.

Blood Sugar Fluctuations

Research from the University of Bath suggests strong black coffee on an empty stomach, particularly after poor sleep, can impair blood sugar control. The study found a 50% increase in blood sugar response to a subsequent meal. This may lead to energy spikes and crashes. Those with insulin sensitivity or diabetes should take note.

Potential Benefits of Coffee on an Empty Stomach

While there are risks, some people note benefits, often in specific contexts such as intermittent fasting or pre-workout routines.

Faster Caffeine Absorption: Rapid absorption on an empty stomach can provide a quick energy boost and improved mental clarity for those who tolerate it.
Fat Burning: Consumed before a morning workout, caffeine on an empty stomach may enhance fat-burning by stimulating the nervous system.
Appetite Suppression: Caffeine's appetite-suppressing effect can be more noticeable on an empty stomach.

Comparing the Effects: Empty vs. Full Stomach


Aspect	Coffee on an Empty Stomach	Coffee After Breakfast/With Food
Caffeine Absorption	Faster and more intense, leading to a quick "kick."	Slower and more gradual, resulting in a milder, more sustained energy boost.
Digestive Impact	Can cause increased stomach acid, irritation, heartburn, and reflux.	Food acts as a buffer, reducing the acidic effects and risk of irritation.
Hormonal Response	Can cause a larger spike in cortisol (the stress hormone), potentially leading to anxiety.	The cortisol response is typically more moderated, leading to a calmer experience.
Blood Sugar Control	Can temporarily impair glucose tolerance, especially after poor sleep, leading to spikes and crashes.	Promotes better glucose regulation and more stable energy levels throughout the morning.
Appetite	Can suppress appetite, which may lead to skipping breakfast or insufficient calorie intake.	Less impactful on appetite; more likely to be consumed as part of a balanced meal.

How to Mitigate the Negative Effects

If you experience discomfort from morning coffee, consider some changes.

Time Your Coffee Intake

Wait 30 to 60 minutes after waking before your first cup. This allows natural cortisol levels to peak and decline before caffeine intake. Nutritionists often suggest coffee between 9:30 a.m. and 11:30 a.m..

Pair Your Coffee with a Small Snack

Eating a snack or breakfast before or with coffee provides a buffer to help neutralize stomach acid. Options include a banana, toast, oatmeal, or scrambled eggs. Pairing coffee with protein and healthy fats can help stabilize blood sugar.

Choose a Gentler Brew

Cold Brew: Less acidic than hot brew, making it easier on sensitive stomachs.
Darker Roasts: Tend to have lower acidity as the roasting process breaks down acidic compounds.
Decaf: Reduces digestive issues and anxiety if caffeine is the cause.

Consider the Add-ins

Adding milk, cream, or a plant-based alternative can buffer acidity. Plant-based milk is good for those with lactose intolerance.

Conclusion: Is It Bad for Everyone?

For most, coffee on an empty stomach isn't inherently harmful but can cause side effects like digestive discomfort, jitters, hormonal changes, and blood sugar fluctuations, especially for sensitive individuals. Pay attention to your body and adjust timing, preparation, or pair with food if you experience negative symptoms. Finding what works for your body is key.

For more detailed information, refer to resources like the Cleveland Clinic. Is It OK To Drink Coffee on an Empty Stomach?

Frequently Asked Questions

While coffee can temporarily irritate a sensitive stomach by increasing acid production, there is no strong evidence to suggest it causes permanent damage or ulcers in healthy individuals.

For many people, drinking coffee after breakfast is better as food helps buffer the acidity and slows caffeine absorption, reducing the risk of digestive issues, jitters, and blood sugar spikes.

Rapid caffeine absorption when your stomach is empty can intensify its stimulating effects. This can lead to increased heart rate and nervousness, mimicking and sometimes exacerbating anxiety.

Yes, for most healthy people, drinking black coffee on an empty stomach is generally safe. However, it may cause mild stomach irritation or other side effects in those with higher sensitivity to caffeine or acidity.

Eating a balanced breakfast with healthy fats, protein, and fiber can help. Options like a banana, oatmeal, toast, or eggs provide a protective buffer for your stomach lining.

Yes. Cold brewing extracts fewer acidic compounds than hot brewing. This results in a smoother, less acidic coffee that is often easier on the stomach and less likely to cause discomfort.

Many experts suggest waiting about 30 to 60 minutes after waking up before your first cup. This timing allows your body's natural cortisol levels to regulate before introducing caffeine.

During intermittent fasting, black coffee is often permitted as it contains virtually no calories. However, you should still be mindful of potential side effects like acid reflux or anxiety if you're sensitive to it on an empty stomach.