supplementNot FDA-approvedOTC supplement
L-CitrullineBenefits, Dosage & Interactions
L-C-Citrulline is a non-essential amino acid, meaning the body can produce it on its own. It is naturally found in some foods, most notably watermelons, and is also available as a dietary supplement. Research on L-Citrulline focuses on heart and circulatory health and endurance.
How much L-Citrulline do people take?
Pooled trials used roughly 3-9 g daily of L-citrulline (or 6-8 g of citrulline malate). Route reported: Oral. Frequency reported: Once daily, or before exercise in the performance trials. These are amounts documented in the cited studies and labels for L-Citrulline — they are reported for reference, not a recommendation. Regulatory status differs by country, including between the US (FDA) and Canada (Health Canada). Confirm any amount with a licensed clinician before you take it.
See the full reported protocol and its sourcesResearched by DoseRoutine Research TeamReviewed for accuracy by Nicholas Alexander, RSE, SO, PMPLast updated Educational reference only — not medical advice. Always confirm dosing and safety decisions with a licensed clinician.
Evidence: Moderate — Covered by a systematic review, without regulatory approval.
Evidence strengthModerate · 3/4
PreclinicalStrong human evidence
Covered by a systematic review, without regulatory approval.
Plasma half-life
Not applicable
Typical timing
before training
Food rule
on an empty stomach
Default unit
g
What published protocols report
Ranges documented in the literature, shown for reference. DoseRoutine does not recommend an amount — your prescriber or the product label sets the dose.
Reported for L-Citrulline in the cited sources. Published ranges are not dosing advice.
References & evidence
Documents the L-Citrulline entry is written from. Each number matches an inline marker above.
- [1]Effect of L-Citrulline Supplementation on Blood Pressure: a Systematic Review and Meta-Analysis of Clinical TrialsMirenayat MS, Moradi S, Mohammadi H, Rouhani MH · Current Hypertension Reports · 2018 · Peer-reviewed · PMID 30284051
- [2]Effects of L-citrulline supplementation on blood pressure: a systematic review and meta-analysisBarkhidarian B, Khorshidi M, Shab-Bidar S, et al. · Avicenna Journal of Phytomedicine · 2019 · Peer-reviewed · PMID 30788274
References & Evidence
Sources on this page that document L-Citrulline dosing, timing and safety.
- [1]National Center for Biotechnology Information View source
Educational information only — not medical advice. Dose ranges vary by person, indication and prescriber.
What is L-Citrulline studied for?
What is L-Citrulline?Sources for this section: Jumps to this entry in the sources and references list at the end of the page.
L-C-Citrulline is a non-essential amino acid, meaning the body can produce it on its own. It is naturally found in some foods, most notably watermelons, and is also available as a dietary supplement. In the body, L-Citrulline plays a key role in the urea cycle, a process that removes ammonia, a toxic byproduct of protein metabolism, from the body. Beyond this metabolic function, L-Citrulline is a precursor to L-Arginine, another amino acid. L-Arginine is then converted into nitric oxide (NO), a potent vasodilator that helps relax and widen blood vessels. This vasodilation effect is central to many of the proposed benefits of L-Citrulline supplementation, particularly in relation to cardiovascular health and athletic performance. It is commonly marketed as a supplement to support endurance exercise and reduce muscle fatigue. (National Institutes of Health Office of Dietary Supplements, PubChem)
What does the research say about L-Citrulline?
Tap a section to expand.
The primary mechanism of action for L-Citrulline involves its conversion to L-Arginine and subsequent nitric oxide (NO) production. When L-Citrulline is ingested, it is absorbed in the gut and then transported to the kidneys, where it is efficiently converted into L-Arginine. Unlike direct L-Arginine supplementation, L-Citrulline bypasses metabolism in the liver and intestines, leading to a more sustained and elevated increase in plasma L-Arginine levels.
L-Arginine is the sole substrate for nitric oxide synthase (NOS) enzymes, which produce nitric oxide. Nitric oxide is a signaling molecule with various physiological roles, including mediating vasodilation, improving blood flow, and influencing muscle contractility and mitochondrial function. By enhancing NO production, L-Citrulline can contribute to improved circulation, oxygen delivery to tissues, and removal of metabolic byproducts like lactic acid and ammonia during exercise. (National Institutes of Health Office of Dietary Supplements, PubChem)
Source for this section: Sources for How does L-Citrulline work?: Jumps to this entry in the sources and references list at the end of the page.
L-Citrulline is primarily recognized for its potential benefits related to:
* **Enhanced Athletic Performance and Endurance:** By increasing nitric oxide production and blood flow, L-Citrulline may improve oxygen and nutrient delivery to working muscles, while also aiding in the removal of metabolic waste products. This can lead to increased exercise capacity, reduced perceived exertion, and delayed fatigue during high-intensity or prolonged activities. Some research suggests it may enhance power output and improve time to exhaustion. (Mayo Clinic, Cochrane)
* **Reduced Muscle Soreness:** Through its potential to improve blood flow and nutrient delivery, L-Citrulline may contribute to faster recovery and reduced muscle soreness following strenuous exercise. (Cochrane)
* **Cardiovascular Health:** The ability of L-Citrulline to increase nitric oxide and promote vasodilation holds promise for cardiovascular benefits. This may include supporting healthy blood pressure levels and improving endothelial function, which refers to the health of the inner lining of blood vessels. (MedlinePlus)
* **Erectile Dysfunction:** Given its role in nitric oxide production, which is critical for penile erection, L-Citrulline has been investigated as a potential aid for mild to moderate erectile dysfunction. It may improve blood flow to the penis, thus facilitating erections. (MedlinePlus)
* **Ammonia Detoxification:** As a participant in the urea cycle, L-Citrulline helps the body process and excrete ammonia. This can be particularly relevant during intense exercise, where ammonia levels can rise and contribute to fatigue. (PubChem)
Research on L-Citrulline has investigated its effects across various physiological domains. A review of studies by the National Institutes of Health Office of Dietary Supplements highlights its role in nitric oxide metabolism and potential athletic benefits. A Cochrane review has examined its efficacy in improving exercise performance, noting generally positive but varied outcomes depending on the population and exercise type. Studies cited by MedlinePlus discuss its potential utility in conditions like erectile dysfunction and mild hypertension, attributing these effects to improved nitric oxide signaling and blood flow. PubChem describes the fundamental biochemical pathways involving L-Citrulline, reinforcing its role in the urea cycle and as an arginine precursor. The Mayo Clinic also recognizes L-Citrulline's use in promoting cardiovascular health and athletic performance, often linking it to improved vasodilation.
L-Citrulline is generally considered safe and well-tolerated when taken at recommended dosages. Most reported side effects are mild and may include:
* Gastrointestinal upset, such as nausea, indigestion, or stomach discomfort.
* Diarrhea.
* Bloating.
These effects are more likely at higher doses. Always follow recommended dosage guidelines. This is educational information, not medical advice - consult a qualified clinician before starting, stopping or combining any compound.
Individuals with certain medical conditions should exercise caution or avoid L-Citrulline supplementation:
* **Hypotension (low blood pressure):** Due to its vasodilatory effects, L-Citrulline might lower blood pressure further. Individuals already experiencing low blood pressure should consult a healthcare provider.
* **Kidney disease:** While L-Citrulline is involved in kidney metabolism, individuals with pre-existing kidney conditions should consult their doctor before use.
* **Surgery:** Discontinue L-Citrulline at least two weeks before any scheduled surgery due to its potential effects on blood pressure. This is educational information, not medical advice - consult a qualified clinician before starting, stopping or combining any compound.
L-Citrulline is contraindicated for individuals with known allergies or hypersensitivity to L-Citrulline or any components of the supplement formulation. While generally well-tolerated, its use should be avoided in individuals with severe hypotension or those taking medications for severe blood pressure conditions unless specifically advised by a medical professional. This is educational information, not medical advice - consult a qualified clinician before starting, stopping or combining any compound.
L-Citrulline may interact with certain medications and other supplements, potentially leading to adverse effects:
* **Nitrates:** Products containing nitrates (e.g., nitroglycerin for chest pain) can interact with L-Citrulline, leading to a significant drop in blood pressure. This combination should be avoided.
* **Blood Pressure Medications:** Given its blood pressure-lowering effects, combining L-Citrulline with antihypertensive drugs could lead to dangerously low blood pressure (hypotension).
* **Erectile Dysfunction Medications:** Medications such as sildenafil (Viagra), tadalafil (Cialis), and vardenafil (Levitra) also work by increasing nitric oxide effects and vasodilation. Combining them with L-Citrulline could excessively lower blood pressure.
* **L-Arginine:** While L-Citrulline is converted to L-Arginine, combining high doses of both might excessively augment nitric oxide pathways, especially in sensitive individuals.
Always consult with a healthcare professional before combining L-Citrulline with any other medications or supplements. This is educational information, not medical advice - consult a qualified clinician before starting, stopping or combining any compound.
For athletic performance, L-Citrulline is typically taken approximately 30-60 minutes before a workout. This timing allows for absorption and conversion to L-Arginine, leading to elevated nitric oxide levels during exercise. For general health support or other specific applications, it may be taken at other times, often with meals. It is generally recommended to take L-Citrulline on an empty stomach for optimal absorption, though it can be taken with food if gastrointestinal upset occurs. The user-directed dosage must be set by a licensed clinician.
Source for this section: Sources for When should you take L-Citrulline?: Jumps to this entry in the sources and references list at the end of the page.
Put it into practice
Reading about L-Citrulline is the first step — DoseRoutine helps you act on it. These free tools turn what you just learned into a routine.
What interacts with L-Citrulline?
| Interacts with | Severity | Type | What happens | What to do |
|---|---|---|---|---|
| Any glp1 + supplement | Note | Category ruleConfidence: theoretical | GLP-1 medications slow stomach emptying, changing how/when oral supplements absorb; rapid weight loss raises the importance of protein and micronutrients.Source pending | Time oral supplements when nausea is lowest; prioritize protein and micronutrients; discuss with your provider. |
| Any supplement + medication | Note | Category ruleConfidence: theoretical | Some supplements change how the body processes medications (absorption, liver enzymes, or additive effects).Source pending | Specific pairs are checked against a licensed drug database and shown with their own severity. Always confirm with your provider or pharmacist. |
Frequently asked questions about L-Citrulline
L-Citrulline is the pure amino acid. Citrulline Malate is L-Citrulline bound to malate, a compound involved in energy production. Some research suggests malate may offer additional benefits related to energy metabolism and buffering lactic acid, but the primary active component for nitric oxide production in both forms is L-Citrulline. (DrugBank)
Yes, L-Citrulline is naturally present in several foods, most notably watermelon. Other sources include cucumbers, pumpkins, and other gourds. However, the amounts found in food are generally lower than those typically used in supplement form for performance enhancement. (National Institutes of Health Office of Dietary Supplements)
After ingestion, L-Citrulline is absorbed and converted to L-Arginine. Increases in plasma L-Arginine and nitric oxide levels can typically be observed within 30-60 minutes, with peak effects often occurring around 60-120 minutes. Its half-life in the body is approximately 1 hour. (PubChem)
L-Citrulline is generally considered safe for long-term use in healthy individuals when taken within recommended dosages. However, as with any supplement, periodic consultation with a healthcare professional is advisable, especially for extended use. (National Institutes of Health Office of Dietary Supplements)
Interaction risk for L-Citrulline comes from the rest of the stack: other supplements, prescription medicines, hormone therapy and peptides. Because L-Citrulline is usually taken before training, most avoidable conflicts come from what else lands in that same window. Risk depends on dose, timing and what else is taken the same day, so each pairing has to be checked rather than assumed safe. The free checker at https://doseroutine.com/interaction-checker covers L-Citrulline with no sign-up.
L-Citrulline is typically taken before training. Published protocols usually have it taken on an empty stomach. Published ranges differ between studies and formulations — the dose to use is the one on your label or from your clinician.
There is no single answer for L-Citrulline plus TRT. What matters is the specific protocol you are on and what your most recent hormone panel shows. No general contraindication applies across every TRT protocol, so confirm the combination with the prescribing clinician. See the free TRT interaction reference: https://doseroutine.com/trt-supplement-interactions
Pairing L-Citrulline with peptides has to be assessed one peptide at a time, because GLP-1 agonists, secretagogues, healing peptides and melanocortins do not share an interaction profile. Check the combination peptide by peptide rather than as one group, and review it with a clinician familiar with peptide protocols.
Published frequency for L-Citrulline varies by protocol and formulation, so the label or prescription is what sets it. It is typically taken before training. Most protocols have it taken on an empty stomach. Frequency is a clinical decision, not a fixed rule — confirm it with the prescriber or product label. Comparison of apps that keep a schedule like this: https://doseroutine.com/best-dose-tracking-apps
The effect of a missed dose of L-Citrulline depends on the protocol and formulation you are on. Doubling up to "catch up" is generally not appropriate unless the label or prescriber says so. Follow the missed-dose instructions on your label or from your clinician, and log the miss so the pattern is visible later rather than forgotten.
For L-Citrulline the useful record is the dose, the time it was actually taken, and what else was taken in the same window. A written log or spreadsheet works for planning but does not remind you or flag conflicts — see the honest comparison at https://doseroutine.com/vs/spreadsheet and the wider roundup at https://doseroutine.com/best-dose-tracking-apps — DoseRoutine tracks the schedule, the remaining supply and interactions with the rest of your routine in one place.
Pooled trials used roughly 3-9 g daily of L-citrulline (or 6-8 g of citrulline malate). Route reported: Oral. Frequency reported: Once daily, or before exercise in the performance trials. These are amounts documented in the cited studies and labels for L-Citrulline — they are reported for reference, not a recommendation. Regulatory status differs by country, including between the US (FDA) and Canada (Health Canada). Confirm any amount with a licensed clinician before you take it.
Which studies looked at L-Citrulline?
Peer-reviewed research indexed in PubMed. Each entry links to the original record.
- 1.L-Citrulline Supplementation and Exercise in the Management of Sarcopenia(opens PubMed in a new tab)Nutrients · 2021 · PMID 34579009 · https://pubmed.ncbi.nlm.nih.gov/34579009/
Sources cited on this page
Specific documents referenced by the numbered markers above. Each number matches the marker in the text.
- PubChem CID 9750(opens in a new tab)National Center for Biotechnology Information · pubchem.ncbi.nlm.nih.gov/compound/9750
Verify at
Publisher search links for L-Citrulline. These are places to check the information — they are not citations, so they are not numbered.
- NIH Office of Dietary Supplements(publisher search, opens in a new tab)National Institutes of Health · publisher search
- Mayo Clinic(publisher search, opens in a new tab)Mayo Clinic · publisher search
- Cochrane Library(publisher search, opens in a new tab)Cochrane · publisher search
- DrugBank(publisher search, opens in a new tab)DrugBank Online · publisher search
- PubMed literature search(publisher search, opens in a new tab)National Library of Medicine · publisher search
- DailyMed labeling archive(publisher search, opens in a new tab)U.S. National Library of Medicine · publisher search
- Wikipedia entry(publisher search, opens in a new tab)Wikipedia · publisher search
DoseRoutine compiles summaries from publicly available scientific and regulatory references. Always verify important decisions with a licensed clinician. How we source and review this information.
What is the short answer on L-Citrulline?
Plain-text summary, safe to quote verbatim:
L-C-Citrulline is a non-essential amino acid, meaning the body can produce it on its own. It is naturally found in some foods, most notably watermelons, and is also available as a dietary supplement. Research on L-Citrulline focuses on heart and circulatory health and endurance.
Source: DoseRoutine — https://doseroutine.com/library/l-citrulline
L-Citrulline cheat sheet
DoseRoutine cheat sheet · Supplement
L-Citrulline
L-C-Citrulline is a non-essential amino acid, meaning the body can produce it on its own. It is naturally found in some foods, most notably watermelons, and is also available as a dietary supplement.
Evidence
Moderate
Covered by a systematic review, without regulatory approval.
Studied range
Pooled trials used roughly 3-9 g daily of L-citrulline (or 6-8 g of citrulline malate)
Route
Oral
Frequency studied
Once daily, or before exercise in the performance trials
Half-life
Roughly 1 hour to peak plasma levels
Timing
before training
With food
on an empty stomach
Storage
Cool, dry, sealed
Not FDA-approvedOTC supplementCardiovascularEndurance
Studied ranges, not dosing advice. Not medical advice — talk to a clinician. doseroutine.com/library/l-citrulline
Cite this page
Using this in an article, AI answer, or research note? Please attribute:
DoseRoutine. (2026). L-Citrulline — Overview, Benefits & Side Effects. Retrieved from https://doseroutine.com/library/l-citrulline
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