Creatine vs L-leucine
Written by Aaron CuhaReviewed Sep 2026
The short answer
Two of the cheapest things in the muscle aisle, with very different records. In 30 healthy older men, 7.5 g of leucine a day for three months did not change muscle mass or strength. In mice, leucine did not extend life in either sex, in the same mouse study where rapamycin plus acarbose did better than either drug alone.
- Creatine people
- 168
- Creatine nulls
- 2
- L-leucine people
- 30
- L-leucine nulls
- 1
Dose
No human dose established
Amounts that were given in studies sit in Human evidence on this page. None of them is a personal dose.
3 completed trials, 168 people given it
Dose
No human dose established
Amounts that were given in studies sit in Human evidence on this page. None of them is a personal dose.
1 completed trial, 30 people given it
First-hand reports are counted on each profile and never added together. This page sets two published records side by side. It does not pick a winner.
Column A
CreatineCreatine monohydrate
One of the most studied supplements there is. It clearly boosts strength. Its effect on muscle size is smaller than the ads say, and a European regulator has rejected the claim that it helps thinking.
Column B
L-leucineL-leucine, branched-chain essential amino acid
It did not help mice live longer, in either sex. That was in the same test where rapamycin plus acarbose did better than either drug alone. In 30 healthy older men, 7.5 g a day for three months did nothing for muscle size or strength.
Side by side, on the facts we can check
| What we compare | Creatine | L-leucine |
|---|---|---|
| Category | Muscle & Performance | Muscle & Performance |
| FDA status | Sold as a dietary supplement. Not an approved drug for any use. | A food nutrient the body needs but cannot make, found in all protein in food. Not an approved drug and not approved to treat anything. |
| Half-life | About 3 hours in plasma; muscle stores deplete over roughly 4 to 6 weeks after stopping | Roughly 1 to 2 hours in plasma after an oral dose, which is why leucine is described as producing a pulse of signalling rather than sustained exposure. |
| Molecular weight | 131.1 Da | 131.2 Da. An amino acid. |
| How it works | It fills muscle with phosphocreatine, which refills ATP, the muscle's fast fuel, during hard efforts that last a few seconds. That lets you do more work each session. Most of the strength gain likely comes from that extra work over months, not from creatine building muscle directly. | Leucine is one of three branched-chain amino acids. It is both a building block and a signal. It binds a sensor inside the cell called Sestrin2. That releases a brake and lets the growth switch mTORC1 turn on, which starts muscle protein building. That is why a meal rich in leucine gives a bigger burst of muscle building than a meal with the same protein but less leucine. People call it a trigger, not a supply. Here is the problem for long life. Turning mTORC1 down long-term with rapamycin is the best-repeated way to make mice live longer. Leucine pushes the same switch the other way. |
| Studies in people | 4 | 1 |
| Evidence | Moderate: 3 completed trials, 168 people given it | Limited: 1 completed trial, 30 people given it |
| Legal status, US | Sold as a dietary supplement | Sold as a supplement |
Frequently asked questions
What is the difference between Creatine and L-leucine?
Creatine: One of the most studied supplements there is. It clearly boosts strength. Its effect on muscle size is smaller than the ads say, and a European regulator has rejected the claim that it helps thinking. L-leucine: It did not help mice live longer, in either sex. That was in the same test where rapamycin plus acarbose did better than either drug alone. In 30 healthy older men, 7.5 g a day for three months did nothing for muscle size or strength.
Which has stronger research evidence, Creatine or L-leucine?
Each compound gets a band worked out from facts we counted, with the math shown. Creatine is Moderate (3 completed trials, 168 people given it). L-leucine is Limited (1 completed trial, 30 people given it). That counts how much has been done in people. It does not rate whether either one works, and neither one is called the winner.
Are Creatine and L-leucine FDA-approved?
Creatine: Sold as a dietary supplement. Not an approved drug for any use.. L-leucine: A food nutrient the body needs but cannot make, found in all protein in food. Not an approved drug and not approved to treat anything..
Reviewed Sep 2026. This page puts two published records side by side. It is for learning, and it is not medical advice. When this site shows a dose, it is the dose a trial or a clinic actually used, or what people say they did, with the source attached. None of it tells you what to take.