Separate mass and molar ratios, declared citrulline amounts and batch measurements before comparing a supplement label with an exercise study.
Citrulline malate grams include more than L-citrulline. But “2:1” alone is still insufficient to calculate the L-citrulline amount: a ratio by weight differs from a ratio by moles (numbers of molecules). Compare the declared L-citrulline per serving and the evidence behind that declaration before comparing a product with a study.
These statements answer different questions:
| Label or document entry | What it tells you | What still needs checking |
|---|---|---|
| L-citrulline, with an amount per serving | The declared amount of that ingredient | Serving size and product-specific testing |
| Citrulline malate, with a total amount and 2:1 | Total material and a claimed component ratio | Whether the ratio is by mass or moles; actual component amounts |
| A multi-ingredient blend total | Combined weight of several ingredients | How much citrulline malate, and then how much L-citrulline, it contains |
| An assay percentage | A reported analytical result | What was measured, the method, and whether the result applies to this batch |
Do not assume an undisclosed ratio is 1:1. Do not treat the weight of an entire pre-workout blend as the weight of citrulline malate.
For a hypothetical mixture containing only L-citrulline and malic acid, a 2:1 ratio by mass means two grams of L-citrulline for each gram of malic acid. The L-citrulline fraction is 2 ÷ 3, or about 66.7%.
A 2:1 ratio by moles means two molecular units of L-citrulline per unit of malic acid. PubChem gives molecular weights of 175.19 and 134.09 g/mol, respectively. The theoretical L-citrulline fraction is therefore (2 × 175.19) ÷ [(2 × 175.19) + 134.09], or about 72.3%. PubChem: L-citrulline and malic acid
| Hypothetical two-component material | L-citrulline fraction | L-citrulline in 6 g total |
|---|---|---|
| 2:1 by mass | 66.7% | 4.00 g |
| 2:1 by moles | 72.3% | About 4.34 g |
| Ratio basis unspecified | Unknown | Cannot calculate confidently |
These are composition examples, not recommended servings or measurements of any commercial powder. Added ingredients, moisture and the reporting basis need their own accounting. A percentage for total citrulline malate should not be substituted for the percentage of L-citrulline.
Two papers illustrate why a study's product name is only part of the comparison.
In 2018, Chappell and colleagues used blinded nuclear magnetic resonance spectroscopy (NMR, a chemical analysis method) on five commercial powders described as 2:1. Reported ratios ranged from 1.11:1 to 1.92:1. Repeated measurements of each powder were analytical repeats, not evidence of multiple independently sampled batches per brand.
There is also an unresolved reporting discrepancy: the methods describe molar ratios, while Table 4's component-gram calculations follow mass-ratio arithmetic. We therefore do not use its gram column as a verified conversion for a reader's product. The historical analysis cannot establish the composition of today's batches. Chappell et al., methods and Table 4, 2018
In a 2025 six-week trial, Bayat and colleagues compared plain L-citrulline, citrulline malate and placebo; 33 men completed the study. The two supplement groups received 8 g of plain product or 12 g of malate product. Manufacturer certificates stated 99.5% L-citrulline in the former and 70.0% in the latter: calculated L-citrulline amounts were 7.96 and 8.4 g, respectively.
The researchers explicitly reported no independent chemical analysis. Those amounts are based on the supplied certificates, rather than a separate laboratory confirmation by the research team. They were close, but not identical. Bayat et al., section 2.7 and limitations, 2025
The 2025 study found improvements versus placebo in selected upper-body endurance comparisons, without a significant direct difference between the two citrulline forms. That does not establish formal equivalence, an added benefit from malate, or a universal dose for every lifter. The small male sample, unequal supplement weights and nonstandardized diet limit interpretation. Bayat et al., results and discussion
Composition evidence helps identify what participants received. It does not, by itself, show that a supplement improves strength, muscle growth or your own performance. Our guide to reading human evidence explains how to separate a measured result from a broader claim.
Request the declared L-citrulline amount per serving, the meaning of the ratio, and component-specific results tied to the product's batch. Ask what an assay percentage measures and whether it is reported for the material as supplied or after a dry-weight correction.
If those details are unavailable, keep the comparison uncertain. Do not increase the serving to compensate for an assumed shortfall, especially in a multi-ingredient product. Bring the exact label to a pharmacist or sports dietitian when deciding whether a supplement fits your situation. Clearer composition information supports a better comparison; it does not certify effectiveness or safety.
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