A handful of supplements have solid evidence behind them for building muscle, but most of what you’ll find on store shelves does not. Creatine monohydrate and protein supplements sit at the top of the list with decades of research. A few others, like beta-alanine, caffeine, and HMB, play supporting roles depending on your training level and goals.
Creatine Monohydrate
Creatine is the single most effective supplement for gaining lean muscle mass. When combined with resistance training, it adds an average of 1.1 kg (about 2.4 pounds) of lean body mass compared to training alone, based on a large meta-analysis of randomized clinical trials. That gain holds across age groups. Without exercise, creatine does essentially nothing for muscle size, adding a negligible 0.03 kg on average.
The gains are more pronounced in men, who added an average of 1.46 kg of lean mass with creatine, while women saw a smaller, statistically non-significant increase of about 0.5 to 0.6 kg. That doesn’t mean creatine is useless for women. It likely still helps, but the effect is smaller and harder to detect in studies.
Creatine works by replenishing your muscles’ immediate energy supply during short, intense efforts like lifting weights. This lets you squeeze out a few more reps per set, which adds up over weeks and months into more total training volume and, ultimately, more muscle growth. The standard approach is 3 to 5 grams per day, taken consistently. A loading phase of 20 grams per day for five to seven days can saturate your muscles faster, but it’s not required.
As for safety, creatine is well studied. The Mayo Clinic notes it is likely safe at recommended doses for up to five years. Studies in healthy people have not found that creatine harms kidney function. The common concern about kidney damage stems from the fact that creatine raises creatinine levels in your blood, which is a marker doctors use to assess kidney health. But that elevation is a byproduct of creatine metabolism, not a sign of kidney damage. People with existing kidney disease should talk to their doctor before using it.
Protein Supplements
Protein powder isn’t magic. It’s a convenient way to hit the daily protein intake your muscles need to grow. If you’re already eating enough protein through whole foods, adding a shake on top won’t produce extra gains. The value is purely practical: it’s fast, portable, and easy to dose precisely.
The amount that matters most is protein per meal, not just the daily total. Research on lean mass and strength shows the strongest association when you eat 30 to 45 grams of protein per meal, spread across at least two meals per day. A classic study found that 30 grams of protein from a single serving of beef was enough to maximally stimulate the muscle-building response, and going higher than that in one sitting didn’t further increase it. The key amino acid driving that response is leucine, which acts as a trigger for muscle protein synthesis. Older adults generally need about 3 grams of leucine per meal to hit that threshold, while younger adults can get by with slightly less.
Whey vs. Casein
Not all protein powders are equal. Whey protein stimulates muscle protein building more effectively than casein, at least in the hours immediately after drinking it. In a study comparing the two in older men, whey produced a muscle protein synthesis rate of 0.15% per hour compared to 0.08% per hour for casein. Whey digests and absorbs faster and contains more leucine per gram, which is why it triggers a stronger anabolic response. Casein digests slowly and provides a more sustained trickle of amino acids, which is why some people take it before bed. For most people, whey is the better default choice around training.
Caffeine
Caffeine won’t build muscle directly, but it can help you train harder, which builds muscle indirectly. A meta-analysis found that even very low doses (roughly 1 to 2 mg per kilogram of body weight, taken about 60 minutes before exercise) produced measurable improvements in muscular strength, muscular endurance, and movement velocity. For a 175-pound person, that’s as little as 80 to 160 mg, roughly the amount in one to two cups of coffee.
The effect sizes are modest. You’re not going to add 50 pounds to your squat overnight. But consistently training with slightly more intensity and volume session after session compounds into real muscle growth over months. If you already drink coffee, you likely already get this benefit.
Beta-Alanine
Beta-alanine helps with exercises that last roughly one to four minutes by buffering acid buildup in your muscles. It’s the burning sensation you feel during high-rep sets or sustained efforts. Over time, supplementing with beta-alanine increases levels of a compound called carnosine in your muscles, which absorbs that acid and delays fatigue.
The catch is that it takes a long time to work. Carnosine levels can take more than 12 weeks to fully maximize. The recommended dose is 5 to 6 grams per day, split across meals (roughly 2 grams with breakfast, lunch, and dinner) to minimize the harmless but sometimes uncomfortable tingling sensation it causes on your skin. Beta-alanine is most useful if your training involves a lot of higher-rep work or circuit-style training. For someone doing low-rep, heavy strength work, the benefit is minimal.
HMB
HMB is a byproduct your body naturally produces when it breaks down the amino acid leucine. Its primary benefit isn’t building muscle so much as preventing muscle loss. It helps slow protein breakdown, which makes it most useful in two situations: when you’re new to training and experiencing significant muscle damage from unfamiliar exercise, or when you’re older and fighting age-related muscle loss.
A meta-analysis in Frontiers in Nutrition found that 3 grams per day, taken for more than 12 weeks and combined with exercise, significantly increased lean mass and grip strength in adults over 50. The effects were most prominent in people over 65. For younger, trained lifters who are already eating enough protein and getting plenty of leucine, HMB offers little additional benefit. At that point, you’re essentially supplementing with a tiny fraction of what leucine already provides.
Omega-3 Fatty Acids
Fish oil won’t pack on muscle in young, well-fed lifters. But for older adults, omega-3 fatty acids (the kind found in fatty fish and fish oil supplements) may help muscles respond better to protein and exercise. Research shows that 8 weeks of omega-3 supplementation at about 3.4 grams per day enhanced the muscle-building signaling pathway and protein synthesis rates in healthy adults around age 71. Omega-3s also appear to improve isometric strength, possibly by enhancing how nerve signals reach your muscle fibers.
If you’re under 40, eating a decent diet, and training consistently, fish oil is unlikely to noticeably improve your muscle gains. If you’re over 50 and finding that your muscles don’t respond to training the way they used to, omega-3s are a reasonable addition.
What Doesn’t Work as Well as Marketed
Most supplements marketed for muscle building fall into a gray zone of weak evidence or effects so small they’re not worth the cost. Branched-chain amino acids (BCAAs) were popular for years, but if you’re eating enough total protein, they add nothing. You’re already getting BCAAs from whole protein sources like whey, meat, eggs, and dairy. Testosterone boosters made from herbal extracts like tribulus or fenugreek have repeatedly failed to show meaningful effects on muscle mass in controlled studies. Glutamine, another popular ingredient, is abundant in a normal diet and supplementing with more hasn’t been shown to improve muscle growth in healthy people.
The supplements that actually work are relatively cheap and unsexy. Creatine monohydrate costs pennies per serving. Whey protein is a commodity product. Caffeine is available in every kitchen. The ones that cost the most per serving and promise the most dramatic results are almost always the ones with the weakest evidence.
Putting It Together
If you’re starting from scratch, protein and creatine are the only two supplements worth buying right away. Hit 30 to 45 grams of protein per meal across at least two meals, take 3 to 5 grams of creatine daily, and train consistently. That covers the vast majority of what supplementation can do for muscle growth. Add caffeine before training if you find it helps your performance. Consider beta-alanine if your training style involves a lot of sustained, high-rep work. Save HMB and omega-3s for specific situations like aging-related muscle loss or recovery from periods of inactivity. Everything else is optimization at best and a waste of money at worst.