This article is written by Amy from The Running Dietitian. Many runners start their day with a cup of coffee out of routine and to help wake themselves up before a morning run. But, they may not know that the cup of joe (specifically the caffeine) is doing more than just providing a wake up call.

Caffeine can be a powerful tool for runners, especially when it comes to endurance running. It helps delay fatigue by supporting muscle contractions and improving how efficiently your body produces energy. Just as importantly, caffeine works on the brain by blocking signals that make you feel tired, which boosts alertness, focus, and even mood.

This combination reduces how hard a run feels, making it easier to hold your pace for longer. Caffeine may also help your body use more fat for energy in the early stages of exercise, conserving glycogen for later in the run. Together, these effects mean caffeine can help you feel better, run farther, and perform stronger on race day.

The most important thing to remember is to focus first on maintaining a nutritious, balanced diet to fuel your training, and only introduce caffeine if it works for you!

Caffeine intake does not come without risks. Some runners experience gastrointestinal issues such as an upset stomach or diarrhea when they take caffeine before a run or race. Others may notice side effects like heart palpitations, jitters, anxiety, or headaches.

Timing can also play a role in side effects. Taking caffeine too late in the day may disrupt sleep, which can negatively affect your body’s recovery process. The best way to minimize these risks is to practice with caffeine during training so you know how your body reacts before relying on it in competition.

While caffeine can be beneficial for runners, there are times when it’s best to limit or avoid it. Conditions such as high blood pressure, heart arrhythmias, or the use of certain medications can increase sensitivity to caffeine’s effects. Pregnant or breastfeeding individuals may also face restrictions. It’s always best to consult your healthcare provider to determine what’s right for you. Although generally safe for adults, caffeine is not recommended for children.

When it comes to dosage, more is not always better. The International Society of Sports Nutrition recommends 3 to 6 milligrams of caffeine per kilogram of body weight, taken about 60 minutes before exercise. Higher doses, especially above 9 milligrams per kilogram, are more likely to cause the side effects mentioned earlier.

On a daily basis, most adults should keep caffeine intake under about 400 milligrams, which is the equivalent of four cups of coffee. It is also important to keep in mind that individual response varies widely: genetics, habitual intake, and personal sensitivity all impact how strongly someone experiences the benefits or risks of caffeine.

Caffeine timing can play a big role in how effective it is for performance. The most common strategy is to consume 3-6mg per kg of body weight of caffeine about 60 minutes before exercise. This allows the concentration of caffeine to peak as you begin the race.

Timing plays a big role in how effective caffeine is for performance. The standard strategy is to consume it about an hour before exercise so that blood concentrations peak as you start running. For races that last several hours, like a marathon, one pre-race dose may not be enough. Since caffeine’s half-life is about four to five hours, many marathoners benefit from topping off with 50 to 100mg throughout the race to delay fatigue.

Because caffeine takes time to work, the timing of these top-offs matters more than the distance alone. For example, a caffeinated gel taken around mile 18 will be much more useful than one at mile 24, when the race is nearly over. Adjusting the number and timing of gels to match your finish time, overall intake, and personal tolerance is key to finding the right strategy.

Here's an example plan for for using non-caffeinated and caffeinated gels during a marathon:

(Everyone is different. Adjust based on your finish time and total caffeine tolerance.)

Run Gum: Delivers caffeine through the lining of your mouth, so it kicks in faster than coffee or capsules and avoids potential stomach upset. It’s also portable and easy to take right before, or even during a run.

Coffee: One of the most popular pre-run caffeine sources and can deliver anywhere from 80-200 mg of caffeine per cup depending on the brew.

Flow Formulas Drink Mix with Caffeine: Along with 135mg caffeine in 2 scoops, it will also help meet pre-run carbohydrate needs.

Carbs Fuel Caffeinated Gel: Supplies 100 mg of caffeine plus carbs, making it a convenient all-in-one fueling option.

The bottom line is that caffeine can be a valuable tool for endurance runners when used wisely, but it is different for everyone. By delaying fatigue, improving focus, and making race pace feel easier, it can improve performance and increase the chances of running your goal time on race day.

However, the key is to practice with caffeine during training to find the right dose, timing, and source that works for your body. More isn’t always better, and the best strategy is the one that helps you run your strongest while avoiding unwanted side effects.