L-Arginine and L-Citrulline
Each entry’s own grades, side by side. A grade says how strong the evidence is for one outcome — it does not rank one entry over the other.
Compound or practice
L-Arginine
The direct nitric-oxide precursor that mostly loses to citrulline because the gut destroys it first.
Grade C3 graded outcomesrevised Jul 10, 2026
A structured monograph in Prometheus's bundled library. Its grades are the monograph's own reading of the evidence, not a peer-reviewed review.
Compound or practice
L-Citrulline
The arginine route that actually absorbs — a legitimate pump-and-reps pre-workout with modest blood-pressure benefit.
Grade B3 graded outcomesrevised Jul 10, 2026
A structured monograph in Prometheus's bundled library. Its grades are the monograph's own reading of the evidence, not a peer-reviewed review.
Graded in both
Outcomes are matched by name. Two entries can describe the same outcome in different words, so one listed further down may still be graded in the other.
| Outcome | L-Arginine | L-Citrulline |
|---|---|---|
| Blood pressure | Evidence grade CSmall effectmixedModest reduction | Evidence grade BSmall effectmixedModest reduction |
Graded only in L-Arginine
- Erectile function Small effectEvidence grade C
- Exercise pump / performance Trivial effectEvidence grade D
Graded only in L-Citrulline
- Resistance reps / pump Small effectEvidence grade B
- Endurance performance Small effectEvidence grade C
Conditions
Only in L-Arginine
- Erectile dysfunction May improveEvidence grade C
Only in L-Citrulline
None.
What each entry says about the other
- L-Arginine’s entry · Works together: Citrulline raises arginine more effectively — sometimes combined.
- L-Arginine’s entry · Goes with: Citrulline raises arginine more effectively — sometimes combined.
Both columns are read from the entries as they stand in this library. A comparison is not advice to take either one, and it is no substitute for a clinician who knows the person.