Ingredient guide · fitness

L-Citrulline

Nitric oxide precursor for pumps & endurance

The clinically studied dose

6g per day Clinical

Source: Examine.com — Citrulline — ~6–8 g L-citrulline (or 8 g citrulline malate) pre-exercise for blood-flow/performance.

What it is

An amino acid that converts to arginine and boosts nitric oxide — better than taking arginine directly.

What the research supports

How it works

Raises plasma arginine and nitric oxide, widening blood vessels during exercise.

Human evidence

Added roughly 3 extra reps to failure vs placebo — a real but small effect (SMD ≈ 0.20).

Meta-analysis of 12 RCTs · n=198 · 6–8 g citrulline malate, ~60 min pre — Vårvik et al., 2021 — Int J Sport Nutr (meta-analysis)

Reduced post-exercise rating of perceived exertion and muscle soreness; blood-lactate effects were inconsistent.

Meta-analysis of RCTs · n=~180 · 6–8 g — Rhim et al., 2020 — J Sport Health Sci (meta-analysis)

Bottom line: A small, genuine bump in reps-to-failure and reduced soreness at 6–8 g — nothing dramatic, and several trials find nothing at all. The visible 'pump' is extra blood flow, largely cosmetic rather than performance.

Side effects & safety

Very safe, even at high doses. Occasional mild stomach upset. Note: 'citrulline malate' is only ~50–65% citrulline by weight.

What users report COMMUNITY · ANECDOTAL

Polarizing
Distilled from 3 top r/Supplements threads (230 comments) on r/Supplements · read the threads yourself →
✓ Reported benefits
someA noticeable gym pump at 6 g+ for some
⚠ Reported downsides
notedA recurring niche complaint: citrulline → arginine can trigger cold sores / herpes / shingles flares in prone people (balance with lysine)
commonOtherwise close to no side effects
🤨 The skeptic take
strong consensusEffective dose is ~7–10 g — most pre-workouts underdose it, and 'malate' numbers inflate the real citrulline
notedHelps the gym pump but not ED / erections for several users

Anecdotes, not evidence, and not medical advice. Frequency labels are our read of forum sentiment, not a formal survey. Individual responses vary widely.

What it should cost

Per serving
Typical branded single-ingredient product$0.87
Bulk powder at the clinical dose (500g, $26.97)$0.32

Buying bulk powder instead of a branded bottle saves about 63% per serving.

Bulk price: $26.97/500g → Alt source: $15.99/500g

Graded products that contain it

Related ingredients

Educational only — not medical advice. Grades and clinical doses are computed from public labels against sourced research (citations on the main site); prices last verified 2026-07-21. Expensive Powder has no sponsors; bulk links may earn an affiliate commission, which never affects a grade. Talk to a clinician before starting any supplement.