L-Citrulline

Non-essential amino acid that converts to arginine, superior for nitric oxide production and cardiovascular health

Scientific nameL-Citrulline FormulaC6H13N3O3 Molecular weight175.19 g/mol CAS372-75-8

95 absorption score

9 safety / 10

35 USD per month

5 documented interactions

Check it against something

Evidence level A

L-Citrulline with:

82 out of 100

Works better together Take together — same timing window amplifies the synergy.

Check it against your whole stack →

What it does

mechanism and evidence for each claim

Superior athletic performance enhancement

More effective than arginine for exercise performance and muscle pumps

Better absorption and conversion to arginine than direct arginine Evidence A-grade 1-2 weeks

Enhanced cardiovascular health

Supports healthy blood pressure and circulation

Sustained arginine and nitric oxide production Evidence A-grade 2-6 weeks

Improved muscle pumps and vascularity

Enhances muscle blood flow and exercise-induced pumps

Increased nitric oxide production improves muscle perfusion Evidence A-grade 30 minutes to 2 hours

Reduced muscle soreness and fatigue

Decreases exercise-induced muscle damage and soreness

Improved blood flow enhances nutrient delivery and waste removal Evidence B-grade 1-4 weeks

Enhanced erectile function

Superior to arginine for male sexual health support

Better sustained nitric oxide production for penile blood flow Evidence B-grade 2-8 weeks

Others take these for the same thing

Same goal, different mechanism — check any of them against this one

Creatine Monohydrate Strength & power enhancement 3-5g A 95% Calcium Bone health & muscle function 1,000-1,200 mg A 30% Magnesium Glycinate Superior absorption sleep & muscle support 200-600 mg A 90% Coenzyme Q10 (CoQ10) Heart health & cellular energy 100-200mg A 10% Fish Oil (EPA/DHA) Heart & brain health 1-2g EPA/DHA A 85% Psyllium Husk Digestive health & cholesterol support 5-15g A 95%

Every pair we checked

12 combinations scored by the engine

L-Citrulline + L-Lysine May compete with citrulline-derived arginine Needs attention 58

L-Citrulline + Caffeine No documented interaction either way No known interaction 70

L-Citrulline + Creatine Monohydrate No documented interaction either way No known interaction 70

L-Citrulline + Calcium Carbonate No documented interaction either way No known interaction 70

L-Citrulline + Whey Protein No documented interaction either way No known interaction 70

L-Citrulline + Lactase No documented interaction either way No known interaction 70

L-Citrulline + Bovine Collagen No documented interaction either way No known interaction 70

L-Citrulline + DHA No documented interaction either way No known interaction 70

L-Citrulline + Turmeric No documented interaction either way No known interaction 70

L-Citrulline + Vitamin D3 Protects nitric oxide from oxidative damage Works better together 78

L-Citrulline + Citrulline Malate Malate enhances energy production and reduces fatigue Works better together 82

L-Citrulline + Beetroot Powder Complementary nitric oxide production pathways Works better together 86

Dosage

Pre workout

Daily3-8g

Athletic performance6-8g pre-workout

Cardiovascular health3-6g daily

Acute performance8-10g single dose

Maintenance3-6g daily

Before you take it

VeganYes

When to expect it

First Effects30 minutes to 2 hours for acute performance benefits

Peak Benefits1-4 weeks for sustained cardiovascular and performance benefits

Deficiency DevelopmentRarely deficient as body produces adequate amounts

Toxicity OnsetVery rare, mainly digestive upset

How to measure it

$80-150

MarkerPlasma citrulline, arginine, or nitric oxide metabolites

OptimalCitrulline: 20-40 μmol/L, Arginine: 50-150 μmol/L

Deficient belowCitrulline: <15 μmol/L

FrequencyOnly if monitoring cardiovascular or athletic performance

What people actually reported to the FDA

CAERS, 7 reports naming it as the suspect

Most reported effects

Blood disorder 2

Erectile dysfunction 2

Heart rate increased 2

Heart valve incompetence 2

Insomnia 2

Named as the suspect 7 reports of 10 that mention it at all

Serious outcome 92% hospitalisation, emergency room or worse

Life Threatening4

Other Serious or Important Medical Event3

Disability2

Reports are voluntary and unverified — they record what someone experienced while taking something, not what the compound caused. Counts skew towards products people take a lot of, and a serious outcome is more likely to be reported than a mild one, so these are not rates. How we filter them →

What actually reaches you

The label counts the carrier, your body does not

Absorption Very high 95 of 100 · best absorbed form of this compound

Delivered daily 5225 mg

Cost per 100 mg delivered $0.02 comparative — uses the absorption score, not a measured percentage

Works better with

3 documented

Citrulline Malate

Malate enhances energy production and reduces fatigue

Malate supports Krebs cycle and ATP production · level A

Beetroot Nitrates

Complementary nitric oxide production pathways

Different NO pathways provide additive effects · level B

Vitamin C

Protects nitric oxide from oxidative damage

Antioxidant protection preserves NO function · level B

What not to take with L-Citrulline

2 documented

High Arginine Doses

May compete for absorption pathways

Competition for amino acid transporters · mild significance

Lysine High Dose

May compete with citrulline-derived arginine

Lysine competes with arginine for uptake · mild significance

Medication interactions

Discuss these with a pharmacist before combining

blood-pressure-medications Moderate

May enhance blood pressure lowering effects

What to do: Monitor blood pressure, may need dose adjustments

pde5-inhibitors-viagra Moderate

May enhance effects and risk of low blood pressure

What to do: Use caution, monitor for hypotension

nitrate-medications Minor

May enhance nitrate effects

What to do: Monitor for enhanced drug effects

Available forms

bioavailability compared

L-Citrulline (Free Form) 95

L-Citrulline (Free Form): Superior to arginine, Excellent absorption, Athletic performance, Cardiovascular support

Food sources

before you supplement

Watermelon 0.7-1.0g per cup · 85

Watermelon rind Higher concentration than flesh · 80

Cucumbers Low amounts · 75

Other melons Moderate amounts · 75

Too little

deficiency signs

Rarely deficient as body produces adequate amounts:
Poor exercise performance and recovery
Suboptimal circulation and blood flow
Reduced exercise-induced muscle pumps
Poor cardiovascular health markers

Too much

toxicity signs

Excellent safety profile:
Mild digestive upset with very large doses
Potential blood pressure effects
Generally very well tolerated

Who benefits most

athletes-performance-enhancement

Superior for exercise performance, pumps, and endurance

6-8g 30-60 minutes pre-workout

cardiovascular-health

Supports healthy blood pressure and circulation

3-6g daily (divided doses)

bodybuilding-muscle-pumps

Enhances muscle blood flow and exercise-induced pumps

6-8g pre-workout

erectile-dysfunction

Superior to arginine for male sexual health support

3-6g daily

endurance-athletes

Reduces fatigue and improves exercise capacity

6-8g before training

Where to buy it

compare forms first

Look for L-Citrulline at 3-8g per serving. The form that matters here is L-Citrulline (Free Form).

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How it works

Converted to arginine in kidneys bypassing liver metabolism
Sustained arginine production leads to prolonged nitric oxide synthesis
Not metabolized by arginase enzyme that degrades arginine
Enhances endothelial nitric oxide synthase activity
Improves ammonia disposal through urea cycle participation
Increases plasma arginine levels more effectively than arginine itself

Key findings

what the evidence supports

Superior to arginine for raising plasma arginine and nitric oxide
Effective for athletic performance enhancement and muscle pumps
Supports cardiovascular health and healthy blood pressure
Excellent safety profile with minimal side effects

Sources: NIH Examine.com · data reviewed 2026-08-02

Compiled by Denis, who maintains this database and holds no medical qualification — every figure here is sourced or derived, never asserted. How we calculate it →

Common questions

What are the benefits of L-Citrulline?

Documented effects: Superior athletic performance enhancement; Enhanced cardiovascular health; Improved muscle pumps and vascularity; Reduced muscle soreness and fatigue. More effective than arginine for exercise performance and muscle pumps

How much L-Citrulline should you take per day?

The common daily range is 3-8g. By goal — athletic performance: 6-8g pre-workout; cardiovascular health: 3-6g daily; acute performance: 8-10g single dose; maintenance: 3-6g daily.

When is the best time to take L-Citrulline?

Pre workout. First effects are typically reported within 30 minutes to 2 hours for acute performance benefits.

What are the side effects of L-Citrulline?

At excessive doses: Excellent safety profile:, Mild digestive upset with very large doses, Potential blood pressure effects, Generally very well tolerated. Safety rating at normal doses is 9 out of 10.

What should you not take with L-Citrulline?

Separate it from High Arginine Doses, Lysine High Dose by two to four hours. May compete for absorption pathways

Does L-Citrulline interact with medications?

Documented interactions with blood-pressure-medications, pde5-inhibitors-viagra, nitrate-medications. Discuss these with a pharmacist before combining.

How do you know if you need L-Citrulline?

The marker is Plasma citrulline, arginine, or nitric oxide metabolites, optimal range Citrulline: 20-40 μmol/L, Arginine: 50-150 μmol/L. Common deficiency signs: Rarely deficient as body produces adequate amounts:, Poor exercise performance and recovery, Suboptimal circulation and blood flow, Reduced exercise-induced muscle pumps.

Taken for

52 Heart

Fish Oil (EPA/DHA) · EPA · Olive Oil Extract

43 Performance

Caffeine · Creatine Monohydrate · Whey Protein