Extreme Endurance begins working in your system within 48-72 hours, as confirmed by over 14 years of clinical testing. 

Testing shows that the longer you are on Extreme Endurance, the greater the benefits.

Elite athletes have used Extreme Endurance for 12+ years straight.

Extreme Endurance can be taken together with almost every other supplement but you do not need to take any product containing Beta Alanine when taking Extreme Endurance.

We also recommend that you do not take additional magnesium supplements and if you have a question on dosage please reach out to info@xendurance.com.

Most active people and those that train hard get an adequate amount of magnesium with the daily dose of Extreme Endurance.

You do not need to take Extreme Endurance with food.

Extreme Endurance was the very first US sports nutrition supplement certified and tested for banned substances by LGC; Informed Sport.

LGC is a world-renowned sports doping control and research laboratory, with over 50 years of expertise in anti-doping in sport. LGC has published over 300 scientific papers on methods for the detection of trace levels of substances that are prohibited in sport and has over 450 man-years of research into doping control.

LGC has been testing supplements and ingredients on behalf of reputable manufacturers and suppliers for over 15 years. It has tested tens of thousands of samples during this time and has also carried out a number of research studies to explore the prevalence of contamination with prohibited substances in products and ingredients.

LGC's research into supplements and contamination also includes several administration studies to investigate the levels of prohibited substances that could cause an athlete to fail a doping test. These have been published in peer-reviewed scientific journals. As a doping control laboratory, LGC works directly with sports authorities, national anti-doping organizations, and national governing bodies worldwide.

There are no NCAA approved supplements. The NCAA does not approve supplements.


Since 2007, Xendurance has had over a million NCAA student-athletes take Xendurance products. These student athletes rely on the Informed Sport certification which is a global testing method for banned substances.

Xendurance was the first US sports nutrition company to use Informed Sport for certifications.

Over the years we’ve discovered that some individuals with highly acidic diets may experience interference with the dissolution of Extreme Endurance. However, everyone is unique—one of our athletes drinks 12 cups of coffee a day and thrives on Extreme Endurance with excellent results!

For those who drink acidic beverages such as juices and more than one or two cups of coffee per day, we recommend consuming caffeine and juices one or two hours after consumption to help ensure optimal effectiveness.

You do not need to cycle on and off with Extreme Endurance.

Clinical studies, since 2008, show the longer you are on Extreme Endurance the greater the benefits. Elite athletes have been using Extreme Endurance for 12+ years.

Doing a baseline test when starting Extreme Endurance offers valuable data to establish a "baseline," allowing you to measure the benefits of this unique supplement. Below are some examples of baseline tests, which can be applied to almost any sport for accurate tracking.

Cyclists: Time yourself on a stationary bike measuring wattage and heart rate. Take Extreme Endurance for 10 days and remeasure. 

Strength and Conditioning: Choose three exercises to do at 80% max and do as many as possible, timing yourself. Go on Extreme Endurance for one week and do as many as you can of these three exercises, again, at 80% max while timing yourself, and you will see the benefits.

Ex: bench press to failure at 80% max, then go to squats, and let’s say you squat 200 lbs, do 80% or 160 lb squats to failure, and immediately go to pull-ups and go to failure.

We encourage a parent to email info@xendurance.com and provide the sport and activity level of their child and their age, and weight. We can then provide better guidance for the parent as to the experience we have seen with athletes using the product under the age of 18.

We do not recommend anyone under the age of 14 use Extreme Endurance.

The most important thing to remember when taking Extreme Endurance is to take it consistently like you would a multivitamin.

You can split the morning and evening dosage to the time of the day that works best for you. Ex; If you take it at 6 am and 5 pm, we encourage you to try to take it around 6 am and 5 pm everyday.

The normal dose of Extreme Endurance is 6 tablets per day: 3 in the morning and 3 in the evening.

For athletes preparing for a significant event, such as an ultra-distance race, a state meet, or any event more intense than usual, we recommend implementing a “load dose.” This involves increasing your dosage to 8 tablets per day—4 in the morning and 4 in the evening—starting 7-10 days before the event. Continue this dosage for one day after the event, then return to the regular dose of 6 tablets per day.

It is important to note that Extreme Endurance should be used on a daily basis to see best results. We have had elite athletes on Extreme Endurance for 12+ years.

In 2008, our pro-triathletes began using the load dose and reported achieving their best results with this approach. Based on their success, we now recommend the load dose strategy for competitors across all sports.

Since 2008, we've heard from athletes across nearly every sport imaginable—except curling! We're still waiting for a curler to share their experience. So, if you're a curler, we’d love to hear from you! From runners, ultra-distance athletes, marathoners, and triathletes to CrossFit enthusiasts, cyclists, Jiu Jitsu fighters, swimmers, tennis players, golfers, surfers, football players, basketball players, baseball players, motocross riders, paddleboarders, skiers, boxers, rugby players, rock climbers, wrestlers, and hockey players—the list goes on. Just not curling… yet!