Supplements for Muscle Growth: What Actually Works

One supplement on this page is worth your money for muscle: creatine monohydrate. Its case for strength and power output is grade A — the International Society of Sports Nutrition calls it "the most effective ergogenic nutritional supplement currently available to athletes with the intent of increasing high-intensity exercise capacity and lean body mass during training."¹ For muscle size specifically it's a grade B, because it amplifies what your training builds rather than building anything on its own.

That is the ceiling of this category, and it's lower than the supplement aisle implies. Everything else is either food you could have eaten, a performance aid that was never a muscle builder, or a claim with no study attached. Meanwhile the biggest supplement-shaped lever in the whole conversation — how much protein you eat in a day — is a grocery decision, not a purchase.

Protein comes first, and it isn't really a supplement

The largest meta-analysis on the question pooled 49 studies and 1,863 participants: adding protein supplementation to resistance training produced 0.30 kg more fat-free mass (95% CI 0.09–0.52) and 2.49 kg more on 1RM strength (95% CI 0.64–4.33) than resistance training alone.³ Small numbers — and the reason they're small is the finding that matters. The same analysis identified a breakpoint at roughly 1.6 g of protein per kg of bodyweight per day (95% CI 1.03–2.20), past which extra protein contributed nothing further to training-induced gains in fat-free mass.³ The authors reported that breakpoint even though the underlying segmental regression missed statistical significance (p = 0.079)³ — so treat 1.6 g/kg as a well-supported target, not a precisely located cliff edge.

The ISSN lands in the same place: an overall daily intake of 1.4–2.0 g/kg/day "is sufficient for most exercising individuals" to build and maintain muscle, delivered in doses of about 0.25 g/kg or 20–40 g, spread every 3–4 hours across the day.⁴ For an 80 kg lifter, that band works out to roughly 110–160 g of protein a day.

Read those two findings together and the practical conclusion is unglamorous. A protein shake works because it's a cheap, convenient way to hit a daily number — not because powder does something meat, eggs, dairy, or beans don't. If you're already eating around 1.6 g/kg, another scoop is buying you convenience, not muscle. If you're at half that, fixing it will do more than any product on this page.

There's no graded protein hub on this site yet, which is why protein doesn't appear in the ranking above. That's a gap in our coverage, not a verdict on protein — it's the first thing to get right.

Creatine monohydrate: the only supplement that earns a slot

Creatine tops the ranking, and it still gets a B for muscle mass. Here's why both of those are true.

The strength case is about as settled as sports nutrition gets, which is where the A lives.¹ The muscle-size case is strong but conditional. In a meta-analysis of 22 randomized trials covering 721 older adults (mean ages 57–70) across programs lasting 7 to 52 weeks, creatine plus resistance training produced 1.37 kg more lean tissue mass than resistance training with a placebo (95% CI 0.97–1.76; p < 0.00001), alongside modest strength gains in chest press and leg press.² That's a real, useful effect. It's also entirely dependent on the training doing the work — creatine adds to a stimulus, it doesn't create one. Some of the earliest scale movement is water pulled into muscle rather than new tissue, which the creatine side effects guide separates out in detail. Genuine amplifier, modest size, training required: that's a B.

How to take it is the least complicated part. Kreider et al. describe the fastest route as about 0.3 g/kg/day for 5–7 days followed by 3–5 g/day to maintain elevated stores¹ — and the loading phase is optional, since daily 3–5 g reaches the same place. Timing is close to irrelevant, which the when to take creatine guide works through. Buy plain monohydrate; the full form-by-form breakdown is on the creatine hub.

On safety, the same position stand states there is "no compelling scientific evidence that the short- or long-term use of creatine monohydrate (up to 30 g/day for 5 years) has any detrimental effects on otherwise healthy individuals."¹ That's a well-studied safety record, and an unusually long one for a supplement. It is not a blanket clearance:

Magnesium: the D on this page

Magnesium is in the ranking because it's the mineral people ask about most under "recovery," and leaving it out would look like an oversight rather than an answer. The answer is no. Nothing supports magnesium building muscle, and the Cochrane review of magnesium for skeletal muscle cramps concluded it is "unlikely that magnesium supplementation provides clinically meaningful cramp prophylaxis to older adults experiencing skeletal muscle cramps."⁸

Magnesium is genuinely worth taking if your intake is short — that case is made benefit by benefit on the magnesium hub. Muscle growth just isn't one of the benefits.

What the rest of the aisle is selling

BCAAs. The definitive review of the question is blunt: "dietary BCAA supplements alone do not promote muscle anabolism," and the claim that they stimulate muscle protein synthesis in humans is "unwarranted."⁵ Whole protein already contains them. If you're hitting your daily protein target, BCAAs are an expensive way to flavor water.

Testosterone boosters. A 2020 review took the first 50 products returned by a consumer search for "testosterone booster" and searched the published literature for each of their 109 distinct ingredients. Of those products, only 24.8% had data supporting their claims, 61.5% turned up no published research on testosterone at all, and 10.1% had data showing a negative effect on testosterone — while 13 of the 50 products exceeded the FDA's tolerable upper intake level for zinc, vitamin B3, or magnesium.⁶ That is close to the definition of a category built on marketing.

Beta-alanine. A real ergogenic aid — and not a muscle builder. The ISSN position stand supports it for performance in open-ended tasks lasting roughly 1 to 4 minutes, at 4–6 g/day for 2–4 weeks; the position statements make no claim about muscle mass or hypertrophy.⁷ Useful if your sport lives in that window. Irrelevant to whether you grow.

Ungraded here. HMB, citrulline malate, betaine, EAAs, "anabolic" pre-workouts, and mass gainers don't have published evidence grades on this site yet, so they don't get ranked or dismissed by us — with one obvious note: a mass gainer is calories in a tub, and calories are cheaper as food.

What actually decides whether you grow

Nothing on this page competes with the four things that do the work: progressive overload over months, enough total calories to build with, enough daily protein, and sleep. Creatine adds to a program that's already working. It cannot rescue one that isn't, and no supplement in this category can. If you're training inconsistently or eating at a deficit, that's where the next gain is — not in a purchase.

Who gets the most from creatine, and who won't notice much

Creatine comes mostly from red meat and fish; a pound of uncooked beef or salmon supplies roughly 1–2 g, and the body needs about 1–3 g/day to keep stores topped up.¹ That's why the biggest responders are people who eat little of either: vegetarians have been reported to have lower intramuscular creatine stores and may therefore see greater gains in muscle creatine from supplementing.¹ Older adults have a specific case too — the 1.37 kg lean-mass result above came from trials in adults aged 57 to 70, where holding onto muscle is tied to staying mobile.²

Who won't notice much: people who already eat a lot of meat and sit near saturation, endurance athletes whose events don't tax the phosphocreatine system, and anyone not training. Creatine amplifies a stimulus. Without one, there's nothing to amplify.

This page is educational information, not medical advice.

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