What Is Caffeine Tolerance?

If you're wondering why your midday pick-me-up doesn't offer the same "jolt" that it had before, you may be experiencing what science calls "caffeine tolerance." But, before we can jump into what caffeine tolerance is, we need to rewind and discuss what role caffeine plays in the body.

According to the US National Library of Medicine, caffeine is a plant-derived stimulant that has many effects on the body ranging from acting as a central nervous system stimulant to a diuretic.

While the initial effects of caffeine on the central nervous system reach a peak level within an hour of consumption, they have the potential to last up to six hours. If you notice the initial one-hour pick-me-up being weaker than it once was, then you may have increased your tolerance to caffeine. Here's how that happened.

How Does Caffeine Tolerance Develop?

Your body is equipped with adenosine receptors in your brain that help regulate sleep, arousal, and cognition. Caffeine blocks the adenosine molecules from binding to these receptors, thus allowing you to feel the "energy" burst that often coincides with caffeine consumption.

However, according to nutrition expert Lindsey Janerio, RDN, owner of NutritiontoFit.com, "Caffeine tolerance develops with routine caffeine consumption. This increases the number of adenosine receptors which, in turn, decreases the effects of caffeine, creating a caffeine tolerance."

While an early animal study from the 1980s that notes the increase in adenosine receptors with chronic caffeine exposure is still cited throughout literature, very few present-day studies are conducted using humans as test subjects due to the serious side effects of consuming too much caffeine.

How Much Caffeine is "Too Much?"

There is no one size fits all approach in deciding how much caffeine is safe for each individual and their personal health. Everyone is unique in how fast they will be able to metabolize and break down caffeine, so it's important to understand your own tolerance. Most healthy individuals can tolerate one cup of coffee or alternate caffeinated beverage without a problem. However, the only way to really know your tolerance to caffeine is to explore and take note of how your body responds after consuming it.

According to the recent Dietary Guidelines for Americans (DGA), every life stage has specific recommendations regarding caffeine consumption, such as limiting consumption if you are pregnant and/or breastfeeding or avoiding completely if you are under two years old.

With that said, there really is no "recommended" amount to consume established for the general public. Rather, the Food and Drug Administration (FDA) and the DGA have established that up to 400 mg of caffeine a day (roughly the equivalent of four to five cups of coffee) is unlikely to be associated with any negative and dangerous side effects in the average healthy person.

Registered dietitian Jessi Holden, MS, RDN, of Holden Nutrition, shares that not all types of caffeine have the same effect on the body. "Those who have (or are at risk of developing) cardiovascular disease or hypertension may want to be more cautious of their consumption of caffeine from tea due to the research that shows an increase in cardiovascular disease events."

Similar effects have also been seen with energy drinks. According to the National Center for Complementary and Integrative Health (NCCIH), increased consumption of energy drinks and smaller energy shots have doubled the number of emergency room visits and hospitalizations between 2007 and 2011.

Energy drinks often contain caffeine as well as other ingredients that have additional caffeine, so it's hard to decipher the actual amount of caffeine in these drinks. This poses a safety issue. Plus, consumption of these beverages may result in increased heart rate and blood pressure alongside sleep disturbances, digestive problems, and dehydration.

How To Know If You Have Caffeine Tolerance

While the research in this area is limited, both Janerio and Holden share the same theory when discussing caffeine tolerance: if you notice caffeine does not affect you in the same way it has before, then it's likely you have developed caffeine tolerance.

Holden explains, "If you're someone who drinks one cup of coffee to start your day because you like that it makes you more alert, but overtime notice that the same one cup of coffee doesn't quite do it for you so you drink more, you likely have developed a caffeine tolerance. Pretty soon, you might drink an extra cup in the morning and require a caffeine boost in the afternoon. Personal experience tells me that we just have to examine our habits and take a close look at our caffeine intake and how we tolerate it."

How to Counteract Caffeine Tolerance

Again, there is no one-size-fits-all approach to lessen the effects of caffeine tolerance, but you should be aware that any drastic decrease in caffeine consumption may result in something known as a caffeine withdrawal.

During a caffeine withdrawal, you may experience headaches, nausea, irritability, difficulty concentrating, and/or sleepiness. While these symptoms may sound unpleasant, they usually disappear within a few days.

Janerio recommends slowly decreasing the amount of caffeine you are consuming over time to build up the response you once found from caffeine consumption. She does not recommend increasing your caffeine consumption to counteract the effects of your tolerance, as this could have a potentially lethal result.

Dangers of Caffeine Tolerance

Having a high caffeine tolerance may become dangerous for specific individuals.

If you begin to experiment with different supplements, powerful energy drinks, and/or medications that contain large amounts of caffeine, you may experience some negative side effects that can be lethal depending on the dose you have consumed.

If you have developed a high tolerance level for caffeine, you may not be as in tune with the side effects that caffeine produces, such as dehydration, anxiety, and/or abnormal heart rhythms.

A Word From Verywell

Although it's unlikely for healthy individuals with no preexisting conditions to have negative side effects if their caffeine consumption remains under the recommended 400 mg per day, we still do not know the long-term effects that caffeine tolerance poses. It's recommended to speak with a healthcare provider if you are concerned about your caffeine consumption and potential health risks.