Can I take pre-workout supplements while on a GLP-1 medication?

Pre-workout supplements (“pre-workouts”) are products that are designed to provide the body additional energy and can assist in endurance performance during intense sports and exercise. Many individuals in the fitness space tout pre-workouts as essential for building muscle, burning fat, and sky-rocketing performance. But how important are they for general fitness and are they safe to take while on a GLP-1 medication? Let’s dive in.

Many pre-workouts include ingredients like beta-alanine, caffeine, branched-chain amino acids, and citrulline, to name a few. While some pre-workouts combine these ingredients, other supplements are sold as isolated ingredients. Here we review pre-workout supplements with strong scientific consensus and touch on a few that may not be worth the hype.

While pre-workout supplements may boost performance, we should think of them like icing on a cake. Other factors like adequate nutrition, hydration, and sleep build the foundation for strong exercise performance, while pre-workout supplements are a bonus and are not a replacement for adequate nutrition, hydration, and sleep.

• Adequate nutrition: Consuming enough protein, carbohydrates, fiber from fruits and vegetables, and eating enough in general are key for fueling your workouts. Sufficient intakes of iron and omega-3 fatty acids can also support athletic performance.
• Hydration: Even just two percent fluid loss can decrease energy metabolism and cognition by up to five percent. While needs vary from person to person, aiming to consume half of your weight in ounces is a good start.
• Sleep: Research shows that lack of sleep leads to decreases in physical performance across the board. This means that your workouts may feel harder and you may experience decreased strength, decreased reaction time, increased risk of injury, and poor recovery from exercise.

According to our physicians, pre-workout supplements are safe to take while on weight loss medications, including GLP-1s. However, since GLP-1 medications work by delaying gastric emptying, it’s important to note that some medications may prolong or delay the effects of pre-workout supplements like caffeine. For some, artificial sweeteners that are often found in pre-workout supplements may also cause mild gastrointestinal distress like gas, bloating, or abdominal discomfort.

Despite many pre-workout supplements claiming to have “fat-burning effects,” a pre-workout supplement likely won’t trigger your body to burn fat. Rather, pre-workout supplements can help to boost performance in the gym, allowing you to maintain a higher level of effort in your workouts. In some cases, some pre-workout supplements may actually lead to short-term increases in weight. But fear not! These increases are largely due to water retention rather than fat gain.

Current research shows strong support for creatine monohydrate, beta-alanine, caffeine, and dietary nitrates as performance-enhancing supplements.

Creatine Monohydrate

• What is it? Creatine is a naturally occurring compound found in skeletal muscle that is produced by the liver, kidneys, and pancreas from building blocks of proteins called amino acids. Small amounts of creatine can also be found in animal-based foods like meat and fish. Creatine monohydrate is one of the most widely studied and supported performance supplements.
• How does it work? Creatine promotes the production of adenosine triphosphate (ATP), an essential compound that stores and delivers energy to cells in the body. When we refer to “energy” we’re actually referring to ATP. Research suggests that creatine supplementation increases the amount of creatine (and thus ATP) that is available to working muscles. These effects increase exercise capacity and training adaptations leading to increases in training volume, lean muscle mass, and muscular strength and power. Creatine’s benefits appear to be less noticeable in elite athletes than folks who are new to exercise.
• What is it best for? Creatine supplementation is primarily recommended for individuals who engage in power and strength exercises like weight lifting and in sports that involve intermittent sprints or repeated high-intensity exercise like soccer or basketball. Creatine may also improve recovery from high-intensity exercise, aid in injury prevention, and improve tolerance to exercising in heat. Research also shows that creatine may help improve blood sugar control for resistance trained individuals, may have beneficial effects on mood and cognition, and may improve outcomes for individuals being treated for depression, but more research is needed in these areas.
• What are the common side effects? Creatine supplementation may cause short-term increases in body weight. These changes are likely due to water retention since creatine drives additional water into muscle cells and are not due to fat gain. Stomach cramping can occur if creatine is supplemented without sufficient water, and diarrhea can occur if too much creatine is supplemented at once.
• What else should I know? Human studies on creatine supplementation have failed to find any significant adverse effects of creatine supplementation on the liver or kidneys, however individuals should always consult with their physician before supplementing.
• How and when should I take it? Individuals can saturate their creatine stores by following a loading phase including four 5-gram doses of creatine (20 grams per day) for five to seven days to increase muscle creatine stores, followed by a maintenance dose of 3-5 grams per day even on rest days. A loading phase isn't necessary, however, and individuals can achieve the same creatine saturation over a longer period of time by consuming a maintenance dose. Research shows it’s best to take creatine monohydrate before or after exercise (~30 minutes), and that taking creatine after exercise may have a larger effect on muscle growth than taking it beforehand.
  
  

Beta-alanine

• What is it? Beta-alanine is a non-essential amino acid that is produced in the liver and is found in fish, poultry, and meat.
• How does it work? During exercise, the body breaks down sugar in the form of glucose into lactic acid, which is converted into lactate. This process lowers the pH of muscle tissue and reduces the muscles’ ability to contract, leading to fatigue. Beta-alanine increases the concentration of an amino acid called carnosine in the muscle. Carnosine acts as a buffer and reduces the acidity of muscle tissue during high-intensity exercise, leading to less overall fatigue as a result.
• What is it best for? Research shows the greatest benefits of beta-alanine have been demonstrated in bouts of high-intensity exercise like high-intensity interval training or short sprints lasting for 1 to 10 minutes, with the most pronounced effects in 1-4 minutes. These effects are seen regardless of fitness level or type of exercise. Beta-alanine may lead to average performance increases of 2-3%, which may not pose much value for the average individual but can be the difference between winning and losing for competitive athletes like boxers. Supplementing with beta-alanine has shown to have no effect on body composition in football players and wrestlers, men who were new to resistance training, and recreationally active females, so opting for adequate nutrition and considering creatine supplementation may be a better approach for those with body composition goals.
• What are the common side effects? A tingling sensation called paresthesia in the face, neck, shoulders, and arms is a common side effect that may occur 15 minutes to one hour after ingestion. Consuming smaller divided doses of about 1.6 grams may lessen these effects.
• How and when should I take it? Daily supplementation of 4 to 6 grams per day for at least two to four weeks has been shown to improve exercise performance. Beta-alanine is safe to consume 15 to 20 minutes before a workout on an empty or full stomach, however consuming beta-alanine with a meal can further increase carnosine levels. Supplementing with beta-alanine even on rest days is considered to be safe.
  
  

Caffeine

• What is it? Caffeine is a naturally derived stimulant found in coffee, tea, and soda, and is often included in pre-workout supplements because of its ability to increase both aerobic and anaerobic performance.
• How does it work? Caffeine acts as an adenosine receptor antagonist meaning that it blocks the action of adenosine, a compound that causes sedation and relaxation. As a result, caffeine can promote alertness and increase dopamine, which has stimulating and mood-enhancing effects.
• What is it best for? Caffeine has been shown to benefit athletic performance for short-term high intensity exercise and endurance based-activities by enhancing vigilance during bouts of long intense exercise, improving mood states, lowering perceived exertion, and decreasing perception of muscle pain. Research also suggests that caffeine can spare carbohydrates during exercise leading to improved endurance exercise capacity and may even increase strength.
• What are the common side effects? Caffeine increases the perception of alertness and wakefulness, and can induce feelings of anxiety in some individuals especially at high doses. Some individuals don’t respond well to caffeine and may experience symptoms like restlessness/shakiness, insomnia, headaches, dizziness, increased heart rate, irritability, and difficulty focusing even at low doses. Caffeine also has appetite suppressing effects. For those on a GLP-1 medication who are struggling to eat enough, be sure to be mindful of caffeine intake and avoid overconsumption of caffeine as it may cause additional appetite suppression.
• How and when should I take it? Plasma caffeine levels typically peak within 60 minutes of consumption, so aiming to consume caffeine 45 to 60 minutes before exercise is key. According to the International Society of Sports Nutrition, doses of 2 to 6 milligrams per kilogram of body weight are safe, however most individuals see benefits with a lower dose. (This would be 135 to 405 milligrams for someone who weighs 150 pounds.) For individuals with higher body weights, we recommend capping caffeine ingestion at 400 milligrams rather than utilizing bodyweight as a tool to determine intake. An average cup of coffee contains around 95 milligrams of caffeine, so 1 to 2 cups will likely support performance.
• What else should I know? Some concern has been expressed that ingestion of caffeine prior to exercise may contribute to dehydration, although several studies have not supported this concern. The FDA considers 400 milligrams of caffeine to be a safe amount for daily consumption, but some pre-workout supplements may exceed this amount in a single serving or may not disclose the amount on their label. Many of caffeine’s effects are subject to tolerance and may not occur in people who have adjusted to caffeine no matter how large the dose is.
  
  

Dietary nitrates

• What is it? Nitrate is a small molecule that the body produces in small amounts and is found in vegetables like beetroot, turnips, and leafy greens.
• How does it work? Nitrates help to regulate blood flow and blood pressure, helping to enhance time to exhaustion, muscle contraction, and maximal force output in exercise. When we consume them, dietary nitrates are converted to nitrite by gut bacteria and then to nitric oxide by the stomach.
• What is it best for? Nitrates show the greatest benefits in exercise ranging from 1 to 10 minutes particularly in anaerobic cardiovascular exercise or muscular endurance exercise like hockey, rugby, rowing, and some CrossFit exercise. Nitrates also have a benefit for prolonged cardiovascular exercise (like a 5K jog or a 10K bike ride) to a lesser extent.
• What are the common side effects? Consuming beets may change the color of urine or stool anywhere from pale pink to bright red. Itchiness or rash may result from excessive consumption.
• How and when should I take it? Nitrates don’t exist as an isolated dietary supplement due to regulations against high quantities of sodium nitrate—a food additive found in meat products. Rather, nitrates should be consumed through a pre-workout meal that contains leafy greens or beetroot or through beetroot juice around 2 to 3 hours before exercise to allow the conversion of nitrate to nitric oxide. The optimal dose of nitrate supplementation is 6.4 to 12.8 milligrams per kilogram of body weight, which would be 440 to 870 milligrams for someone who weighs 150 pounds.
• What else should I know? Individuals should refrain from using mouthwash during nitrate supplementation as this can interfere with bacteria in the mouth that help with the conversion of nitrate to nitric oxide. Highly trained individuals may be less likely to experience the effects of nitrate supplementation.

• Citrulline: Citrulline is an amino acid that helps the body produce nitric oxide and improve blood flow. While it’s often included in pre-workout supplements, the research on citrulline’s effect on exercise performance is mixed. For example, two meta-analyses found that citrulline supplementation did not improve strength or aerobic exercise performance, while other meta-analyses found that citrulline supplementation reduced rating of perceived exertion, decreased muscle soreness, and increased total reps completed during resistance training. (Our consensus: We may need more research on citrulline before we know how it impacts exercise performance.)
• Branched-chain amino acids (BCAAs): Amino acids are the building blocks of protein. Of twenty amino acids, nine are considered essential since the body can’t make them. Three essential amino acids have a “branched-chain” chemical structure including leucine, valine, and isoleucine. BCAA supplements that include these three amino acids are touted for their ability to stimulate the muscle building process (called muscle protein synthesis). However, research continues to show that the process of building muscle requires all nine essential amino acids. Consuming BCAAs alone won’t improve muscle growth. Instead, focusing on meeting your daily protein needs through high-quality sources is key. Most animal proteins except collagen contain all nine essential amino acids. For those who follow a vegan/vegetarian diet, consuming a diverse diet with special attention to plant-based protein sources can ensure that daily protein needs are met. (Our consensus: BCAAs are probably not necessary for exercise performance based on current research.)
• Glutamine: Glutamine is a conditionally essential amino acid, meaning the body needs more glutamine than it can produce under certain conditions like illness, injury, or surgery. While glutamine supplementation may support other conditions (like IBS for example), it is often marketed as an exercise supplement. However, there are no consistent observed effects on athletic performance from glutamine supplementation to date. (Our consensus: Glutamine is probably not beneficial to exercise performance based on current research.)
• Tart cherry juice: Tart cherry juice has been shown to accelerate recovery after exercise and decrease markers of inflammation following both strength and endurance training. While not a pre-workout supplement per se, incorporating tart cherry juice after repeated bouts of strenuous exercise may help individuals recover quickly from exercise (although acute stress following training is beneficial for training adaptations). Consuming tart cherry juice before exercise may offer a source of carbohydrates to boost performance. Tart cherry juice may also influence melatonin levels and promote sleep. (Our consensus: Tart cherry juice may be worthwhile to incorporate into your workout regimen based on current research.)

For a full guide on what to look for when choosing a dietary supplement, read our article on how to choose supplements.

Adequate nutrition, hydration, and sleep are key, but pre-workout nutrition can also boost performance.

• 5-15 minutes before exercise: Focus on quick-digesting carbohydrates like dates, honey, or even a small serving of juice. Those sugars will provide the body quick energy that will be used in exercise.
• Up to 1 hour before exercise: Focus on carbs that are easy to digest like a piece of fruit and incorporate enough healthy fats to keep you satisfied. Fat is the slowest macronutrient to digest and too much may cause digestive discomfort, so testing your individual tolerance is key. Examples include a banana with peanut butter or energy bites that include oats, maple syrup, and nut butters. If you’re resistance training, adding small amounts of protein (like Greek yogurt) before a workout may help the muscle building process.
• 2-3 hours before exercise: For workouts longer than one hour, aim to eat a complete meal with carbs, protein, fiber, and healthy fats two to three hours before exercise like an egg omelet with whole-grain toast, a few slices of avocado, and a cup of fruit.

• The best way to boost performance in the gym is through adequate nutrition, hydration, and sleep.
• Some pre-workout supplements like creatine may lead to short-term increases in weight due to water retention rather than fat gain.
• Beta-alanine may lead to a tingling sensation called paresthesia in the face, neck, shoulders, and arms 15 minutes to one hour after ingestion. Consuming smaller divided doses of about 1.6 grams may lessen these effects.
• Some supplements have stronger scientific support than others.
• Aim to incorporate one new supplement at time to understand how it may or may not impact your exercise performance rather than adding multiple supplements at once.
• Consult with your health care provider before beginning a new supplement.