Supplement
Citrulline is an amino acid the body converts into arginine, which it uses to make nitric oxide, a molecule that relaxes blood vessels. People most often look at it for erectile dysfunction, where the evidence is moderate, including a randomized trial in men with mild cases. For athletic performance, small studies found no clear difference in aerobic or anaerobic measures, so that evidence is very limited.
Sources: PMID 21195829
- Updated
- How we grade
- 45 studies cited
- Best evidence
- Grade B
- Conditions studied
- 22
- Outcomes
- 169
- Graded outcomes
- 02811
Evidence by condition
- Strong
- Moderate
- Limited
- Very limited
General Cardiovascular Health
Cardiovascular Disease
- Blood Pressure: improves
- Plasma Arginine: improves
Eisenmenger Syndrome
- Blood Pressure: improves
- Exercise Capacity: improves
Pulmonary Hypertension
- Blood Pressure: improves
- Exercise Capacity: improves
Muscle Recovery
- Blood Flow: improves
- Blood Lactate (Exercise): changes; see studies
- Muscle Soreness: improves
High Blood Pressure
- Arterial Stiffness: improves
- Blood Pressure: improves
- Blood Flow: improves
| Grade | Outcome | Effect | Size | Studies | People | Studies list |
|---|---|---|---|---|---|---|
| Arterial Stiffness Small Improvement | Improves (the measure goes down) | Small effect | 1 study | 41 people | ||
Studies that measured arterial stiffness | ||||||
| Blood Pressure | Improves (the measure goes down) | 7 studies | 155 people | |||
Studies that measured blood pressure
| ||||||
| Blood Flow | Improves (the measure goes up) | 2 studies | 15 people | |||
| Body Fat | Improves (the measure goes down) | 1 study | 41 people | |||
| Heart Rate Variability | Improves (the measure goes down) | 1 study | 40 people | |||
Studies that measured heart rate variability | ||||||
| High-density lipoprotein (HDL) | Improves (the measure goes up) | 1 study | 15 people | |||
| Plasma Arginine | Improves (the measure goes up) | 1 study | 15 people | |||
| Blood glucose | Improves (the measure goes down) | 15 people | ||||
| C-Reactive Protein (CRP) | Improves (the measure goes down) | 15 people | ||||
| Low-density lipoprotein (LDL) | Improves (the measure goes down) | 15 people | ||||
| Nitric Oxide | Improves (the measure goes up) | 15 people | ||||
| Plasma Nitrate | Improves (the measure goes up) | 15 people | ||||
| Total cholesterol | Improves (the measure goes down) | 15 people | ||||
Obesity
- Asthma Symptoms: improves
- Blood Pressure: improves
- Blood Flow: improves
Asthma
- Asthma Symptoms: improves
- Lung Function: improves
| Grade | Outcome | Effect | Size | Studies | People | Studies list |
|---|---|---|---|---|---|---|
| Asthma Symptoms Small Improvement | Improves (the measure goes down) | Small effect | 1 study | 44 people | ||
Studies that measured asthma symptoms | ||||||
| Lung Function | Improves (the measure goes up) | 44 people | ||||
Nonalcoholic Fatty Liver Disease (NAFLD)
- C-Reactive Protein (CRP): improves
- Liver Fibrosis: improves
- Liver Fat: improves
| Grade | Outcome | Effect | Size | Studies | People | Studies list |
|---|---|---|---|---|---|---|
| C-Reactive Protein (CRP) Small Decrease | Improves (the measure goes down) | Small effect | 50 people | |||
| Liver Fibrosis | Improves (the measure goes down) | 1 study | 50 people | |||
| Liver Fat | Improves (the measure goes down) | 50 people | ||||
| NF-kB Activity | Improves (the measure goes down) | 50 people | ||||
| TNF-Alpha | Improves (the measure goes down) | 50 people | ||||
General Athletic Performance
- Aerobic Exercise Metrics
- Anaerobic Capacity
- Blood Pressure: improves
Aerobic Exercise Performance
- Aerobic Exercise Metrics
- Blood Lactate (Exercise): changes; see studies
- Heart Rate: improves
Cycling Performance
- Aerobic Exercise Metrics
- Heart Rate: improves
- Power Output: improves
| Grade | Outcome | Effect | Size | Studies | People | Studies list |
|---|---|---|---|---|---|---|
| Aerobic Exercise Metrics No effect | NoneNo effect | 1 study | 64 people | |||
| Heart Rate | Improves (the measure goes down) | 4 studies | 10 people | |||
| Power Output | Improves (the measure goes up) | 3 studies | 54 people | |||
| Muscular Endurance | Improves (the measure goes up) | 2 studies | 22 people | |||
| Immunity | Improves (the measure goes up) | 1 study | 17 people | |||
| Plasma Arginine | Improves (the measure goes up) | 1 study | 22 people | |||
| Rating of Perceived Exertion | Improves (the measure goes up) | 1 study | 10 people | |||
| DNA Damage | Changes; see studies | 17 people | ||||
| Oxidative Stress Biomarkers | Improves (the measure goes down) | 17 people |
Anaerobic Exercise Performance
- Aerobic Exercise Metrics
- Power Output: improves
| Grade | Outcome | Effect | Size | Studies | People | Studies list |
|---|---|---|---|---|---|---|
| Aerobic Exercise Metrics No effect | NoneNo effect | 1 study | 32 people | |||
| Power Output | Improves (the measure goes up) | 3 studies | 32 people |
Muscle Size Strength
- Anaerobic Capacity
- Blood Pressure: improves
- Blood Lactate (Exercise): changes; see studies
| Grade | Outcome | Effect | Size | Studies | People | Studies list |
|---|---|---|---|---|---|---|
| Anaerobic Capacity No effect | NoneNo effect | 21 people | ||||
| Blood Pressure | Improves (the measure goes down) | 7 studies | 28 people | |||
| Blood Lactate (Exercise) | Changes; see studies | 6 studies | 98 people | |||
| Heart Rate | Improves (the measure goes down) | 4 studies | 28 people | |||
| Power Output | Improves (the measure goes up) | 3 studies | 198 people | |||
| Muscle Soreness | Improves (the measure goes down) | 2 studies | 62 people | |||
| Muscular Endurance | Improves (the measure goes up) | 2 studies | 103 people | |||
| Body Fat | Improves (the measure goes down) | 1 study | 75 people | |||
| Rating of Perceived Exertion | Improves (the measure goes up) | 1 study | 15 people | |||
| Weight | Improves (the measure goes down) | 1 study | 75 people | |||
| Bilirubin | Changes; see studies | 75 people | ||||
| Fatigue Symptoms | Improves (the measure goes down) | 59 people | ||||
| Hemoglobin | Improves (the measure goes up) | 75 people | ||||
| Hydration (Total Body Water) | Improves (the measure goes up) | 75 people | ||||
| Kidney Function | Improves (the measure goes up) | 75 people | ||||
| Liver Enzymes | Changes; see studies | 75 people | ||||
| Muscle Mass | Improves (the measure goes up) | 75 people | ||||
| Muscle Oxygenation | Improves (the measure goes up) | 18 people | ||||
| Red Blood Cell Count | Improves (the measure goes up) | 75 people | ||||
| Serum Albumin | Improves (the measure goes up) | 75 people | ||||
| Strength | Improves (the measure goes up) | 21 people | ||||
| Training Volume | Improves (the measure goes up) | 41 people | ||||
| Urea | Improves (the measure goes up) | 102 people | ||||
| White Blood Cell Count | Improves (the measure goes up) | 75 people |
Metabolic Health
- Blood glucose
- Growth Hormone: improves
- Insulin: changes; see studies
| Grade | Outcome | Effect | Size | Studies | People | Studies list |
|---|---|---|---|---|---|---|
| Blood glucose No effect | NoneNo effect | 17 people | ||||
| Growth Hormone | Improves (the measure goes up) | 2 studies | 25 people | |||
| Insulin | Changes; see studies | 1 study | 37 people | |||
| Plasma Arginine | Improves (the measure goes up) | 1 study | 8 people | |||
| Creatinine | Improves (the measure goes up) | 17 people | ||||
| IGF-1 | Improves (the measure goes up) | 12 people | ||||
| Muscle protein synthesis (MPS) | Improves (the measure goes up) | 12 people | ||||
| Nitric Oxide | Improves (the measure goes up) | 17 people | ||||
| Plasma Glutamine | Improves (the measure goes up) | 29 people | ||||
| Urea | Improves (the measure goes up) | 17 people |
Type 2 Diabetes
- Anti-Oxidant Enzyme Profile
- Total Antioxidant Capacity (TAC): improves
- Blood glucose: improves
| Grade | Outcome | Effect | Size | Studies | People | Studies list |
|---|---|---|---|---|---|---|
| Anti-Oxidant Enzyme Profile No effect | NoneNo effect | 54 people | ||||
| Total Antioxidant Capacity (TAC) | Improves (the measure goes up) | 1 study | 54 people | |||
| Blood glucose | Improves (the measure goes down) | 54 people | ||||
| Oxidative Stress Biomarkers | Improves (the measure goes down) | 54 people | ||||
| Plasma Nitrate | Improves (the measure goes up) | 54 people |
Immune Health
- DNA Damage
- Immunity: improves
- Liver Enzymes: changes; see studies
| Grade | Outcome | Effect | Size | Studies | People | Studies list |
|---|---|---|---|---|---|---|
| DNA Damage No effect | NoneNo effect | 17 people | ||||
| Immunity | Improves (the measure goes up) | 1 study | 17 people | |||
| Liver Enzymes | Changes; see studies | 17 people | ||||
| Oxidative Stress Biomarkers | Improves (the measure goes down) | 17 people |
Tennis Performance
- Anaerobic Capacity
- Power Output: improves
- Strength: improves
| Grade | Outcome | Effect | Size | Studies | People | Studies list |
|---|---|---|---|---|---|---|
| Anaerobic Capacity No effect | NoneNo effect | 21 people | ||||
| Power Output | Improves (the measure goes up) | 3 studies | 21 people | |||
| Strength | Improves (the measure goes up) | 21 people |
Muscle Size & Strength
- Anaerobic Capacity
- Blood Pressure: changes; see studies
- Blood Lactate (Exercise): changes; see studies
| Grade | Outcome | Effect | Size | Studies | People | Studies list |
|---|---|---|---|---|---|---|
| Anaerobic Capacity No effect | NoneNo effect | 21 people | ||||
| Blood Pressure | Changes; see studies | 7 studies | 28 people | |||
| Blood Lactate (Exercise) | Changes; see studies | 6 studies | 98 people | |||
| Heart Rate | Changes; see studies | 4 studies | 28 people | |||
| Power Output | Improves (the measure goes up) | 3 studies | 198 people | |||
| Muscle Soreness | Changes; see studies | 2 studies | 62 people | |||
| Muscular Endurance | Improves (the measure goes up) | 2 studies | 103 people | |||
| Body Fat | Changes; see studies | 1 study | 75 people | |||
| Rating of Perceived Exertion | Improves (the measure goes up) | 1 study | 15 people | |||
| Weight | Changes; see studies | 1 study | 75 people | |||
| Bilirubin | Changes; see studies | 75 people | ||||
| Fatigue Symptoms | Changes; see studies | 59 people | ||||
| Hemoglobin | Improves (the measure goes up) | 75 people | ||||
| Hydration (Total Body Water) | Improves (the measure goes up) | 75 people | ||||
| Kidney Function | Improves (the measure goes up) | 75 people | ||||
| Liver Enzymes | Changes; see studies | 75 people | ||||
| Muscle Mass | Improves (the measure goes up) | 75 people | ||||
| Muscle Oxygenation | Improves (the measure goes up) | 18 people | ||||
| Red Blood Cell Count | Improves (the measure goes up) | 75 people | ||||
| Serum Albumin | Improves (the measure goes up) | 75 people | ||||
| Strength | Improves (the measure goes up) | 21 people | ||||
| Training Volume | Improves (the measure goes up) | 41 people | ||||
| Urea | Improves (the measure goes up) | 102 people | ||||
| White Blood Cell Count | Improves (the measure goes up) | 75 people |
Digestive Health
- Blood Flow: improves
| Grade | Outcome | Effect | Size | Studies | People | Studies list |
|---|---|---|---|---|---|---|
| Blood Flow | Improves (the measure goes up) | 2 studies | 10 people |
Erectile Dysfunction
- Erections: improves
| Grade | Outcome | Effect | Size | Studies | People | Studies list |
|---|---|---|---|---|---|---|
| Erections | Improves (the measure goes up) | 1 study | 24 people |
What the published studies found
6 automated readings
LDL cholesterol
The studies read are too weak to tell whether Citrulline changes LDL cholesterol. They lean toward an improvement, which is not enough to claim one. The evidence is very weak.
1 study counted of 8 read: 1 trial (82 people in the trials).
- Randomised trial, 2023; 82 people; critically ill patients under mechanical ventilation: improves.
low density lipoprotein (LDL-C) (p <0.001)
The Effect of L-Citrulline Supplementation on Outcomes of Critically Ill Patients under Mechanical Ventilation; a Double-Blind Randomized Controlled Trial
- Randomised trial, 2023; 82 people; critically ill patients under mechanical ventilation: improves.
Cardiovascular events
The studies read do not show a clear benefit for cardiovascular events. One reading found evidence too weak to tell, a second reading of the same search found too few studies to tell. The evidence is very weak.
1 study counted of 10 read: 1 trial (269 people in the trials).
- Randomised trial, 2020; 269 people; patients undergoing medium-to-high risk non-cardiac surgery: unclear: evidence too weak to tell.
non-significant trend towards reduced incidence of the primary endpoint
Asymmetric dimethylarginine predicts perioperative cardiovascular complications in patients undergoing medium-to-high risk non-cardiac surgery
- Randomised trial, 2020; 269 people; patients undergoing medium-to-high risk non-cardiac surgery: unclear: evidence too weak to tell.
Endurance performance
Mixed or unclear: two readings of the studies disagreed. One reading found evidence too weak to tell for endurance performance, the other an improvement. The question is open.
7 studies counted of 9 read: 4 reviews and 3 trials (37 people in the trials).
- Meta-analysis, 2026; 30 studies, 644 people: unclear: evidence too weak to tell (the review the verdict rests on).
small improvement in overall exercise performance (g = 0.16, p = 0.01)
Effects of Citrulline Malate Supplementation on Exercise Performance: A Systematic Review and Three-Level Meta-Analysis - Meta-analysis, 2023; 9 studies, 158 people; young healthy adults: no clear difference.
no significant difference in the endurance performance measures
Effects of citrulline on endurance performance in young healthy adults: a systematic review and meta-analysis - Meta-analysis, 2022; 10 studies: no clear difference.
no positive effects of Cit supplementation on aerobic performance
Effects of Citrulline Supplementation on Different Aerobic Exercise Performance Outcomes: A Systematic Review and Meta-Analysis - Meta-analysis, 2021; 3 studies: no clear difference.
No effect on exercise performance following consumption of foods rich in L-citrulline
Effect of food sources of nitrate, polyphenols, L-arginine and L-citrulline on endurance exercise performance: a systematic review and meta-analysis of randomised controlled trials - Crossover trial, 2025; 20 people: no clear difference.
no statistically significant difference in TTE
Ergogenic effects of a 10-day L-citrulline supplementation on time to exhaustion and cardiorespiratory and metabolic responses in healthy individuals: a double-blind, randomised, placebo-controlled crossover trial - Crossover trial, 2020; 9 people; nine trained male cyclists: no clear difference.
improvement in TT time of 5.2%
One Week of L-Citrulline Supplementation Improves Performance in Trained Cyclists - Crossover trial, 2016; 8 people; healthy recreationally-active adult males: no clear difference.
was not significantly different between conditions
Two weeks of watermelon juice supplementation improves nitric oxide bioavailability but not endurance exercise performance in humans
- Meta-analysis, 2026; 30 studies, 644 people: unclear: evidence too weak to tell (the review the verdict rests on).
Muscle strength
Mixed or unclear: two readings of the studies disagreed. One reading found an improvement for muscle strength, the other evidence too weak to tell. The question is open.
8 studies counted of 10 read: 4 reviews and 4 trials (164 people in the trials).
- Systematic review, 2026; 12 studies, 360 people; postmenopausal women: unclear: evidence too weak to tell (the review the verdict rests on).
suggesting improvements only when citrulline was combined
Citrulline supplementation in postmenopausal women: a systematic review of vascular, muscular, and metabolic effects - Meta-analysis, 2022; 4 studies, 138 people; resistance-trained adults: no clear difference.
did not observe an overall effect favoring citrulline-malate supplementation
Effects of Citrulline Malate Supplementation on Muscle Strength in Resistance-Trained Adults: A Systematic Review and Meta-Analysis of Randomized Controlled Trials - Systematic review, 2020; 6 studies, 250 people; older adults aged 50 years and older: improves.
four of six studies reported CIT effects on muscle strength
Effects of Citrulline alone or combined with exercise on muscle mass, muscle strength, and physical performance among older adults: a systematic review - Meta-analysis, 2019; 12 studies, 198 people; healthy men and women: improves.
significant benefit for citrulline compared to placebo treatments
Acute Effects of Citrulline Supplementation on High-Intensity Strength and Power Performance: A Systematic Review and Meta-Analysis - Crossover trial, 2025; 43 people; young, trained men and women: no clear difference.
did not enhance maximal neuromuscular performance
Malate or Not? Acute Effects of L-Citrulline Versus Citrulline Malate on Neuromuscular Performance in Young, Trained Adults: A Randomized, Double-Blind, Placebo-Controlled Crossover Trial - Crossover trial, 2022; 24 people; hypertensive postmenopausal women: improves.
Leg curl strength increased greater with CIT
Combined L-Citrulline Supplementation and Slow Velocity Low-Intensity Resistance Training Improves Leg Endothelial Function, Lean Mass, and Strength in Hypertensive Postmenopausal Women - Randomised trial, 2020; 24 people; healthy young individuals: improves.
significantly larger increase in maximal knee extensor strength
Synergetic Effect of NO Precursor Supplementation and Exercise Training - Randomised trial, 2019; 73 people; sedentary obese older men and women: improves. Initial Dietary Protein Intake Influence Muscle Function Adaptations in Older Men and Women Following High-Intensity Interval Training Combined with Citrulline
- Systematic review, 2026; 12 studies, 360 people; postmenopausal women: unclear: evidence too weak to tell (the review the verdict rests on).
Respiratory infections
Too few usable studies were found to tell whether Citrulline changes respiratory infections. 8 studies were read and none could be counted.
Stress
The best available review (2023, 7 studies) found little or no difference in stress. The evidence is moderate.
1 study counted of 11 read: 1 review.
- Meta-analysis, 2023; 7 studies: no clear difference (the review the verdict rests on).
did not influence inflammatory biomarkers and oxidative stress
Absence of Effects of L-Arginine and L-Citrulline on Inflammatory Biomarkers and Oxidative Stress in Response to Physical Exercise: A Systematic Review with Meta-Analysis
- Meta-analysis, 2023; 7 studies: no clear difference (the review the verdict rests on).
Key findings
- Blood PressureImproves (the measure goes down)
- Arterial StiffnessImproves (the measure goes down)
- Blood FlowImproves (the measure goes up)
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Studies cited
45 studies from PubMed
- l-Citrulline supplementation improves O2 uptake kinetics and high-intensity exercise performance in humans
- Effects of supplemental citrulline malate ingestion during repeated bouts of lower-body exercise in advanced weightlifters
- The Effect of Citrulline/Malate on Blood Lactate Levels in Intensive Exercise
- Citrulline Malate Fails to Improve German Volume Training Performance in Healthy Young Men and Women
- L-citrulline reduces time to exhaustion and insulin response to a graded exercise test
- Effects of Supplemental Citrulline-Malate Ingestion on Blood Lactate, Cardiovascular Dynamics, and Resistance Exercise Performance in Trained Males
- Effects of Citrulline Malate and Beetroot Juice Supplementation on Blood Flow, Energy Metabolism, and Performance During Maximum Effort Leg Extension Exercise
- Eight weeks of resistance training in conjunction with glutathione and L-Citrulline supplementation increases lean mass and has no adverse effects on blood clinical safety markers in resistance-trained males
- Citrulline/malate promotes aerobic energy production in human exercising muscle
- Citrulline malate enhances athletic anaerobic performance and relieves muscle soreness
- Acute Effect of Citrulline Malate Supplementation on Upper-Body Resistance Exercise Performance in Recreationally Resistance-Trained Men
- Acute citrulline malate supplementation improves upper- and lower-body submaximal weightlifting exercise performance in resistance-trained females
- Acute Effects of Citrulline Supplementation on High-Intensity Strength and Power Performance: A Systematic Review and Meta-Analysis
- Acute citrulline-malate supplementation improves maximal strength and anaerobic power in female, masters athletes tennis players
- Impact of L-citrulline supplementation and whole-body vibration training on arterial stiffness and leg muscle function in obese postmenopausal women with high blood pressure
- Impact of l-citrulline supplementation on oxygen uptake kinetics during walking
- Effects of L-citrulline oral supplementation on polymorphonuclear neutrophils oxidative burst and nitric oxide production after exercise
- Oral L-citrulline supplementation enhances cycling time trial performance in healthy trained men: Double-blind randomized placebo-controlled 2-way crossover study
- Acute citrulline-malate supplementation is ineffective during aerobic cycling and subsequent anaerobic performance in recreationally active males
- One Week of L-Citrulline Supplementation Improves Performance in Trained Cyclists
- Oral L-citrulline supplementation attenuates blood pressure response to cold pressor test in young men
- The effects of short term L-citrulline supplementation on wave reflection responses to cold exposure with concurrent isometric exercise
- l-Citrulline supplementation attenuates blood pressure, wave reflection and arterial stiffness responses to metaboreflex and cold stress in overweight men
- Does l-citrulline supplementation improve exercise blood flow in older adults?
- Effect of oral L-citrulline on brachial and aortic blood pressure defined by resting status: evidence from randomized controlled trials
- Acute effects of Nitrosigine® and citrulline malate on vasodilation in young adults
- Acute Citrulline-Malate Supplementation and High-Intensity Cycling Performance
- Oxidative stress and nitrate/nitrite (NOx) status following citrulline supplementation in type 2 diabetes: a randomised, double-blind, placebo-controlled trial
- Improvement of ventricular function in systolic heart failure patients with oral L-citrulline supplementation
- Effect of L-arginine or L-citrulline oral supplementation on blood pressure and right ventricular function in heart failure patients with preserved ejection fraction
- Effect of citrulline on post-exercise rating of perceived exertion, muscle soreness, and blood lactate levels: A systematic review and meta-analysis.
- Citrulline Malate Does Not Improve Muscle Recovery after Resistance Exercise in Untrained Young Adult Men
- L-citrulline improves splanchnic perfusion and reduces gut injury during exercise
- Short-term effects of L-citrulline supplementation on arterial stiffness in middle-aged men
- Inter-Individual Responses to Citrulline Malate Oral Supplementation on Post-Exercise Hypotension in Hypertensives: A 24-Hour Analysis
- Acute Effects of Citrulline Malate Supplementation on Nocturnal Blood Pressure Dipping After Exercise in Hypertensive Patients: A Randomized, Placebo-Controlled Trial.
- L-Citrulline increases nitric oxide and improves control in obese asthmatics
- Chronic l-citrulline supplementation improves cardiac sympathovagal balance in obese postmenopausal women: A preliminary report
- Inflammatory markers response to citrulline supplementation in patients with non-alcoholic fatty liver disease: a randomized, double blind, placebo-controlled, clinical trial
- Oral l-citrulline malate in patients with idiopathic pulmonary arterial hypertension and Eisenmenger Syndrome: a clinical trial
- L-citrulline-malate influence over branched chain amino acid utilization during exercise
- Dose-ranging effects of citrulline administration on plasma amino acids and hormonal patterns in healthy subjects: the Citrudose pharmacokinetic study
- Oral citrulline does not affect whole body protein metabolism in healthy human volunteers: results of a prospective, randomized, double-blind, cross-over study
- Oral L-citrulline supplementation improves erection hardness in men with mild erectile dysfunction
- Nitric oxide precursors and congenital heart surgery: a randomized controlled trial of oral citrulline