The supplements with the strongest evidence for improving workout performance are caffeine, citrulline, and creatine. Beyond those three, a few others can help depending on your training style, but most of what you’ll find in commercial pre-workout blends is either underdosed or unsupported by research. Here’s what actually works, how much to take, and when.
Caffeine: The Most Reliable Performance Booster
Caffeine improves nearly every type of exercise. It enhances muscular endurance, sprint speed, jumping power, throwing performance, and aerobic capacity. For endurance exercise specifically, it consistently improves performance by 2 to 4 percent, which is significant for anyone training seriously.
The effective dose is 3 to 6 mg per kilogram of body weight. For a 70 kg (154 lb) person, that’s roughly 210 to 420 mg. A standard cup of brewed coffee contains about 95 mg, so you’d need two to four cups, or a caffeine pill if you want precision. Take it 30 to 60 minutes before training. Blood levels peak anywhere from 15 to 120 minutes after ingestion depending on what else is in your stomach, so taking it on an empty or lightly filled stomach gets it working faster.
Start at the lower end of the range if you’re not a regular caffeine user. The International Society of Sports Nutrition notes benefits across the full 3 to 6 mg/kg range, so more isn’t necessarily better. One survey of pre-workout users found that 23 percent reported palpitations or accelerated heartbeat, with the average caffeine content of their products around 254 mg. If you experience a racing heart, cut the dose.
Citrulline: Better Blood Flow, More Reps
Citrulline is an amino acid that your body converts into nitric oxide, which widens blood vessels and improves blood flow to working muscles. The practical result is better endurance during sets and reduced fatigue, particularly during high-rep resistance training.
The most commonly studied dose is 6 to 8 grams of citrulline malate, taken 45 to 90 minutes before exercise. You’ll often see it listed as “L-citrulline” or “citrulline malate” on labels. Citrulline malate includes malic acid, so you need a slightly higher dose of it compared to pure L-citrulline to get the same amount of active citrulline. If your pre-workout contains less than 3 grams, it’s likely underdosed. Research has tested doses ranging from 1 to 12 grams, but 6 to 8 grams is the sweet spot for a single pre-workout dose.
Creatine: Essential but Timing Is Flexible
Creatine monohydrate is arguably the most studied supplement in sports nutrition. It increases your muscles’ ability to regenerate energy during short, intense efforts like heavy lifts and sprints. It also supports gains in lean mass over time.
Here’s the thing: creatine doesn’t need to be taken before your workout specifically. It works by saturating your muscles over days and weeks, not by providing an acute boost. A study comparing pre-workout versus post-workout creatine found that post-workout timing was possibly slightly better for gains in lean mass and strength, with the post-workout group gaining 2.0 kg of fat-free mass compared to 0.9 kg in the pre-workout group. But the difference wasn’t statistically significant, and both groups improved.
The standard dose is 3 to 5 grams daily, taken at whatever time is easiest to remember. If you already mix a pre-workout drink, tossing creatine in is perfectly fine. Just don’t skip days, because consistency matters more than timing.
Beta-Alanine: Best for Sustained Efforts
Beta-alanine builds up a buffering compound called carnosine in your muscles, which helps neutralize the acid that accumulates during intense exercise. It’s most effective for efforts lasting 1 to 4 minutes: think 400-meter runs, rowing intervals, or high-rep sets to failure.
Like creatine, beta-alanine works through daily loading rather than acute timing. You need 4 to 6 grams per day for at least two weeks to see a meaningful increase in muscle carnosine (around 20 to 30 percent), with four weeks of loading producing a 40 to 60 percent increase. Split your daily dose into portions of 2 grams or less. Single doses above 800 mg commonly cause a harmless but sometimes intense tingling sensation in the face and hands. A sustained-release formula can reduce this side effect.
If your workouts are mostly heavy, low-rep strength work with long rest periods, beta-alanine won’t do much for you. It shines during the kind of training where your muscles burn and you’re fighting to keep going.
Beetroot Juice: A Surprising Edge for Endurance
Beetroot juice is rich in dietary nitrates, which your body converts to nitric oxide through a different pathway than citrulline. It improves oxygen efficiency, meaning your muscles can do the same work with less oxygen cost. This matters most for endurance activities like running, cycling, and swimming.
The effective dose is 6 to 8 mmol of nitrate, which is roughly what you get in a concentrated beetroot shot (the kind sold specifically for athletes). Nitrate levels in your blood peak 2 to 3 hours after you drink it, with performance benefits observed around 150 minutes post-ingestion. Plan accordingly: if your run starts at 6 PM, drink your beetroot shot around 4 PM. One important note: avoid using mouthwash before taking beetroot juice. The bacteria on your tongue are essential for converting nitrate into its active form, and antiseptic mouthwash kills them.
Highly trained athletes may need a dose at the higher end of the range or slightly above, as the benefits appear to be more pronounced in recreational athletes than in elites.
Electrolytes: Often Overlooked
If you train hard and sweat heavily, you lose meaningful amounts of sodium, potassium, and magnesium. During intense sweating, sodium losses average about 600 mg per hour, with potassium losses around 125 mg per hour and magnesium at roughly 2.3 mg per hour. Sodium is by far the biggest loss.
You don’t necessarily need a special supplement for this. A pinch of salt in your water (about a quarter teaspoon provides roughly 575 mg of sodium) handles the biggest electrolyte concern. If you’re training for over an hour in the heat, adding an electrolyte mix with sodium and potassium is a practical choice. Sipping this in the 30 minutes before and during your workout helps maintain fluid balance and prevent early fatigue from dehydration.
Skip the BCAAs
Branched-chain amino acid supplements (BCAAs) are still widely marketed as pre-workout essentials, but the evidence doesn’t support the hype. A thorough review of the research found no human studies demonstrating that BCAAs alone stimulate muscle protein synthesis when taken orally. In fact, two intravenous studies found that BCAAs actually decreased both muscle protein synthesis and breakdown, leaving muscles in a net catabolic state.
The reason is straightforward: building muscle protein requires all nine essential amino acids, not just the three BCAAs. If you want amino acids before training, essential amino acid (EAA) supplements provide the full set. But if you’ve eaten a meal containing protein within a few hours of training, you already have those amino acids circulating in your blood, making supplementation unnecessary.
A Word on Multi-Ingredient Pre-Workouts
Commercial pre-workout powders bundle many of these ingredients together, which is convenient but comes with trade-offs. Many use “proprietary blends” that hide individual ingredient amounts, making it impossible to know if you’re getting effective doses. A product listing 6 grams of a blend containing citrulline, beta-alanine, and five other ingredients almost certainly underdoses most of them.
There are also safety concerns with stacking stimulants. Products containing synephrine, a compound similar to the banned stimulant ephedrine, have been linked to arrhythmias and dangerously elevated blood pressure, especially when combined with caffeine. Some users report caffeine intake from pre-workouts exceeding 1,300 mg per day when they combine them with coffee or energy drinks. If you use a commercial product, check the caffeine content and count it toward your total daily intake.
Buying individual ingredients and mixing your own pre-workout is cheaper, lets you control doses precisely, and avoids unnecessary filler ingredients. A simple and well-supported stack: 200 to 400 mg caffeine, 6 to 8 grams citrulline malate, and 5 grams creatine, mixed in water 30 to 60 minutes before training.