Taking small, frequent sips, keeping your water bottle clean, and balancing electrolytes are key tips for proper hydration while running.

Take a small sip while running. You might slow down briefly to take a sip during a race, but gulping down large amounts of water at each station can have negative effects.

According to Justin Mullner, a sports physician at the Orlando Health Jewett Orthopedic Institute in Florida, drinking too much water too quickly overloads your stomach, causing it to expand rapidly, which can lead to discomfort and even nausea. Combining running with excessive water intake may further increase the risk of nausea. This is because intense exercise diverts blood flow from the stomach to the muscles, slowing down digestion. “You take in too much water and your stomach can’t process it efficiently,” Mullner explains.

A better strategy is to take small sips of water (or an electrolyte solution) every 15 to 20 minutes, depending on the temperature and running intensity. “This approach helps maintain a steady hydration level and prevents your stomach from feeling overly full,” says Meghan Kennihan, a running coach certified by USA Track & Field, in an interview with Runner’s World.

Start Hydrating Early.

When preparing for a long run or race, many runners forget to hydrate until they’re nearly at the starting line. Kennihan emphasizes that this negatively impacts performance because it doesn’t give the body enough time to absorb and utilize the fluids.

Staying well-hydrated in the days leading up to a long run or race can help you train and compete effectively, avoid feeling overly full, and reduce the need for frequent bathroom breaks. In particular, be sure to hydrate well the day before and check the color of your urine to ensure you’re properly hydrated. “Dark yellow is a sign that you’re not getting enough fluids. Ideally, your urine should be a light yellow,” Mullner explains.

Individual needs vary. Typically, you should drink about 500 ml of water approximately 2 to 3 hours before your run, followed by an additional 250 ml 20 to 30 minutes before heading out. Adjustments may be necessary based on your body size, running distance, and the outdoor temperature.

Keep Your Water Bottle Clean

Using the same water bottle repeatedly means you might be ingesting more than just water. According to Mullner, if you don’t clean your bottle regularly, you could be exposed to bacteria—or even mold.

Every time you bring your mouth to the bottle, or use your hands to open and close it, bacteria can be transferred inside. The moist environment inside a water bottle is an ideal breeding ground for bacteria and mold, especially if you live in a hot and humid area. The U.S. Centers for Disease Control and Prevention warns that if left unchecked, bacteria and mold can continue to grow and potentially cause symptoms similar to food poisoning, such as stomach cramps or nausea, diarrhea, and vomiting. Individuals sensitive to mold may also experience allergic reactions.

Mullner advises that the best practice is to wash your reusable water bottle—whether it’s plastic, stainless steel, or glass—with soap and warm water after each use. “This is even more important if you use your bottle every day or if you’re drinking beverages other than plain water,” he emphasizes. For example, mixing electrolyte powders or adding sports drinks to your bottle introduces more ingredients for bacteria to thrive on.

Mullner notes that visible residue, unpleasant odors, or changes in taste are all signs that your water bottle needs a thorough cleaning.

Balance Your Electrolytes with Water

Staying well-hydrated during long runs and races is crucial, but drinking too much plain water can lead to overhydration.

According to the Cleveland Clinic, hyponatremia—a condition characterized by low sodium levels in the blood—is an extreme form of overhydration. It occurs when the sodium concentration in your blood falls below recommended levels, leading to muscle cramps, headaches, nausea and vomiting, fatigue, and confusion.

Typically, your body maintains electrolyte balance by drawing minerals from your food and excreting excess through urine. However, as explained by the American College of Sports Medicine, intense exercise causes electrolytes—especially sodium—to be quickly depleted through sweat, and hot weather only accelerates this process.

It’s not just newcomers who are prone to dehydration. A 2019 study published in Frontiers in Nutrition found that 41 out of 63 finishers in an ultramarathon experienced mild to severe hyponatremia.

Drinking water without supplementing with electrolytes dilutes the remaining electrolytes, particularly sodium, in your blood. To prevent an imbalance, be sure to include an electrolyte supplement if you’re running for more than 60 minutes or in hot conditions. Carry an electrolyte drink, some gels, or another form of electrolyte supplement with you to keep your body in balance.