Should You Drink Coffee on an Empty Stomach?
More than 90% of people in the United States consume caffeine, and 75% of that group admits to having it daily. Many people say it helps them feel more awake and alert. Coffee is thus the lifeblood of many people’s mornings, serving as a strong, aromatic cup that helps jump-start the day. But, is consuming that morning cup of coffee on an empty stomach a harmless habit, or could it cause some unwanted health effects? Ultimately, drinking coffee likely has the same effects on your body no matter what time of day you consume it.
What Happens When You Drink Coffee on an Empty Stomach?
Studies suggest that after drinking coffee on empty stomach caffeine is absorbed more quickly in the gut, and caffeine levels in the body are higher than when coffee is consumed after eating. As such, drinking coffee first thing in the morning on an empty stomach may cause you to feel the effects of caffeine more rapidly and intensely. That may be a good or bad thing, depending on how caffeine makes you feel.
The Effects of Drinking Coffee on an Empty Stomach
Drinking coffee on an empty stomach is a common habit for many people, but it can have mixed results depending on your body and how sensitive you are to caffeine. Here are some potential effects you might experience:
Increased Acid Production
Coffee contains chlorogenic and citric acids, and when consumed on an empty stomach, it can increase the production of stomach acid. This can lead to feelings of acidity, indigestion, and even heartburn, especially if you are prone to gastrointestinal (GI) issues like irritable bowel syndrome (IBS). However, if you eat breakfast with your coffee, the stomach acid has some food to digest and will ease any adverse Gl symptoms you may experience.
Stimulation of Cortisol Production
Drinking coffee can stimulate the production of cortisol, the body’s stress hormone. Cortisol levels naturally peak in the morning to help you wake up, but consuming coffee on an empty stomach may cause a sharp increase in these levels, leading to heightened stress or anxiety. While coffee may cause a temporary rise in the stress hormone cortisol, it is unlikely to result in health problems—regardless of whether you drink it on an empty stomach or with food.
But, if you find yourself facing experiencing nervousness, dizziness, racing heart beat, or other negative side effects of coffee, eating a snack can help decrease the absorption rate of caffeine and a nutritious breakfast can help balance your cortisol levels throughout the day.
Disruption of Blood Sugar Levels
Drinking caffeine on an empty stomach can cause sharper blood sugar rises because there is no protein, fat, or fiber to buffer the stress-hormone response. Most people see better blood sugar stability when they keep coffee as part of a balanced morning routine, not a replacement for breakfast
Potential for Overstimulation
Since the caffeine in coffee is absorbed more quickly on an empty stomach, you might experience an intense or jittery rush of energy, which can be uncomfortable or even cause anxiety for some people. Caffeine triggers your “fight or flight” stress response, increasing the release of stress hormones like cortisol, epinephrine, and norepinephrine. This response can increase your heart rate, blood pressure and feelings of restlessness — similar to symptoms of anxiety.
Is It Okay to Drink Coffee on An Empty Stomach?
If you experience digestive issues when drinking coffee on an empty stomach, perhaps you can pair it with food. Pairing coffee with a protein-rich snack or meal can also help keep your blood sugar more stable. Ultimately, little scientific evidence, however, suggests that drinking coffee on an empty stomach is harmful.
International Standards for Coffee Quality and Health
When you drink your morning cup of coffee, you may not be thinking about the critical role of international standards in helping oversee product quality from production, roasting, and shipping. Hence, ISO standards govern everything from the types of coffee beans used to how the final product is packaged and sold. Here is a closer look at some of the key ISO standards relevant to coffee:
ISO 3509:2005 – Coffee and Coffee Products Vocabulary
ISO 3509 defines key terms related to coffee, such as “green coffee,” “roast,” and “brew.” It is important because a consistent understanding of these terms assures that the coffee industry can communicate clearly, both within the industry and to consumers.
ISO 18794:2025 – Sensory Analysis of Coffee
ISO 18794 lays out the vocabulary and methods for assessing coffee’s aroma, taste, and other sensory characteristics. Knowing how coffee is analyzed can help us appreciate the nuances of flavor in different types of brews and how they might affect us.
ISO 23134:2022 – Ground Roasted Coffee Particle Size Analysis
Coffee grinding plays a significant role in the brewing process. ISO 23134 outlines a method to analyze the particle size of ground coffee, ensuring a consistent grind. A consistent grind results in a balanced extraction, which impacts the final flavor and strength of your coffee.
ISO 20481:2008 – Caffeine Content Determination
ISO 20481 defines how caffeine should be measured using high-performance liquid chromatography (HPLC), providing accurate and consistent results across different coffee products—including green beans, roasted coffee, soluble (instant) coffee (regular & decaf), and mixed instant beverages like cappuccino.
ISO 8455:2011 – Green Coffee Storage and Transport
ISO 8455 provides guidelines for the proper storage and transport of green coffee beans to prevent infestation and quality loss. Coffee that is stored improperly can lead to unpleasant tastes and potentially cause digestive issues when consumed.
ISO 9116:2025– Green Coffee Sale and Purchase Guidelines
ISO 9116 gives guidance on methods of specification to be used to describe green coffee for sale and purchase. It also gives guidance on procedures for sampling, packing, marking, storage and shipping of green coffee.
Role of ISO Standards in Assuring Coffee Quality
These internationally recognized guidelines help assure coffee is produced, stored, and prepared in a way that maximizes quality and consistency. Whether your preference is to drink coffee on an empty stomach or with food, ISO standards help assure product quality and safety.
You can learn more about ISO standards and coffee in our blog posts: Is There Mold in Your Coffee? Risks, Signs & Staying Safe, ISO 18794:2025—Coffee Sensory Analysis Vocabulary, and ISO 23134:2022—Ground Roasted Coffee.
