Nationals reliever Tyler Clippard typically has an energy drink about the fourth inning of most games. “Just to kinda make sure I’m not falling asleep out there in the bullpen,” he said. “Just to make sure I’m up and attentive.” (John McDonnell/THE WASHINGTON POST)

Over the course of a six-month season, Tyler Clippard has to be ready nearly every game for the bullpen phone to ring and the voice on the other end to call his name. One night, the Washington Nationals reliever and his teammates could be packing up their belongings at 11 o’clock in Denver, and by 3 p.m. the next day they’re walking into the visiting clubhouse in Cleveland. So around the fourth inning of most games, Clippard will reach for a Red Bull or 5-Hour Energy shot.

“Just to kinda make sure I’m not falling asleep out there in the bullpen,” said Clippard, 28. “Just to make sure I’m up and attentive.”

Since Major League Baseball banned amphetamines in 2005, baseball players have noticed an increase in the consumption of energy drinks, which are also a fast-growing portion of the beverage industry. It’s like drinking coffee at your cubicle to provide a boost on another long day at the office, just far stronger, and it can help offset the rigors of a relentless schedule. But it’s not a practice all teams condone. The jump in usage — and dependency — has caught the attention of team and league medical officials.

The Washington Post e-mailed all 30 major league teams about their policy toward energy drinks. Of the 16 teams that responded, none said it banned the caffeine-loaded beverages. Five teams said they do not provide them to players despite the fact that the drinks are legal products and that some meet league standards governing supplements. A few teams, including the Nationals, declined to comment.

Each winter, MLB medical officials remind team doctors, trainers and strength coaches of the dangers of energy drinks.

“If you’re having one, it’s not a big deal,” said Gary Green, MLB’s medical director. “But there are so many things these days that contain stimulants, and my concern is when they start to get combined. That would be a worry. If someone is drinking coffee and then they’re having caffeinated sodas and then they’re using energy drinks and other things, it concerns me. A lot of the problems are dose-dependent.”

And especially around this hot and humid time of the season, high caffeine intake can lead to dehydration, which can put players at a higher risk of muscle cramping, strains or heat-related illnesses. In 2009, Houston Astros reliever Wesley Wright landed in the hospital after reportedly drinking several energy drinks and soft drinks before a game, which led the team to stop providing them for players.

While none of the 16 teams that replied to the e-mail said they ban energy drinks, they don’t exactly encourage their use. The Astros, Arizona Diamondbacks, Cleveland Indians, Baltimore Orioles and Colorado Rockies said they do not provide energy drinks to the players.

The Diamondbacks “discourage” any use of energy drinks, a team spokesman said, while a Rockies spokesman said the club encourages “a multifaceted recovery approach to lessen fatigue and the reliance on caffeinated products.”

An average eight-ounce serving of coffee contains 100 milligrams of caffeine, an 8.4-ounce can of Red Bull contains 83 milligrams and a 5-Hour Energy shot has 215 milligrams, according to a Consumer Reports study.

The American Beverage Association, which represents several companies in the nonalcoholic beverage industry, including Red Bull, Monster and Rockstar, preaches moderation for energy drinks.

“Most energy drinks actually contain significantly less caffeine than a similarly-sized coffeehouse coffee,” an ABA spokeswoman said in an e-mail. “Moreover, caffeine has been safely consumed — in a variety of foods and beverages — around the world for hundreds of years. When it comes to professional athletes, perhaps the most important thing is that they stay hydrated, and our industry provides many options for them to do so.”

Representatives for 5-Hour Energy, which is not represented by the ABA, did not respond to requests seeking comment.

At least six teams only provide drinks that are certified by the National Sanitation Foundation, such as Red Bull. 5-Hour Energy is not NSF-certified and is “strongly discouraged” by the New York Yankees for their players, according to a team spokesman. The lack of the NSF certification, which is paid for by the drinks companies, doesn’t necessarily mean a drink contains MLB-banned substances.

Even some teams that provide energy drinks, such as the Chicago White Sox, are cautious. “Our training staff encourages a ‘food-first’ approach for players regarding energy, and we do stress moderation,” a team spokesman said. The New York Mets “monitor but don’t ban,” according to a team spokesman.

Denard Span, 29, the Nationals’ everyday center fielder, drinks a 5-Hour Energy or Red Bull about 15 minutes before a game to give him “an extra boost.”

“When I feel sluggish, not every day,” he said. “I don’t think it’s good to drink caffeine every day, especially early on. When it’s toward the end of the season, probably drink a little more.”

Some research has shown that caffeine in low doses can boost performance, Green said. In 2004, caffeine was dropped from the World Anti-Doping Agency’s prohibited list and is now on a list of monitored substances.

The NCAA doesn’t allow schools to provide athletes with energy drinks and bans caffeine consumption in high doses.

“We always look at that and consider” banning energy drinks, Green said. “But at this point we probably would not ban that, because it’s a legal substance right now.”

At the heart of baseball players’ usage of energy drinks is the schedule. No other professional sport has such a grinding itinerary. The NFL plays 16 games over four months, the NBA schedules 82 games over 51 / 2 months, the NHL plays 82 games over 71 / 2 months and MLS spreads 34 games out over eight months. None plays as many games per week as professional baseball, and there are side effects. A February study by Vanderbilt University researchers found that players were more likely to swing at pitches outside the strike zone in September than in April, a trend attributed to fatigue that had worsened since the 2005 amphetamine ban.

Some players don’t consume energy drinks out of fear of dehydration or because they don’t need them. Pitcher Mariano Rivera, 43, in his 21st major league season with the Yankees, said he sleeps about seven hours a night and doesn’t consume energy drinks or coffee, relying instead on tea or soda. Teammate Lyle Overbay, 36, who has noticed the spike in energy drink consumption, has tried Red Bull and 5-Hour Energy but doesn’t use either often because he worries about muscle cramping.

“Even when I have a beer or something, my hamstring gets tight,” he said. “I don’t drink very often because of that stuff. And that’s the same thing. I’m not getting any younger either, so I don’t recover as quickly. I can’t really be poisoning my body.”

Span, who doesn’t drink coffee, said he feels more alert with the caffeine from an energy drink. He is careful, especially during summer, to consume more water and electrolyte-filled drinks to stay hydrated.

The reliance on energy drinks, however, isn’t out of a lack in interest in playing baseball daily. Clippard feels the same way.

“As much as it’s a big league game and as much as we’re out there every day grinding, you do it every single day,” Clippard said. “It can become a little monotonous at times. So you just want to make sure you’re locked in every single day. Sometimes it’s easier than others.”