Heart/Performance

L-Citrulline

Nitric oxide–supporting amino acid that may modestly improve blood flow, blood pressure, and exercise tolerance in adults.

L-Citrulline

Nitric oxide–supporting amino acid that may modestly improve blood flow, blood pressure, and exercise tolerance in adults.

score

evidence

Caution

risk

Proven Benefits

01Lowers systolic BP modestly

02Improves exercise performance

03May improve vascular function

04May reduce muscle soreness

05May improve erectile function

06May reduce perceived fatigue

Chemical Forms

Recommended

L-Citrulline (free-form)

Avoid

Citrulline malate with undisclosed ratio
Proprietary pre-workout blends (true citrulline dose often unclear)

Expert Note

Free-form L-citrulline gives the exact dose used in most vascular studies and is well absorbed. Many citrulline malate products do not clearly disclose the citrulline:malate ratio, so the actual citrulline dose may be much lower than the label suggests. Proprietary pre-workout blends often underdose it further.

Protocol

Amount

3-6 g

Frequency

Once daily, or 30-60 minutes before exercise

When

Between meals for vascular use; 30-60 minutes before activity for acute performance effects.

Condition-Based Dosing

High-normal or mildly elevated blood pressure (SBP 120-139 mmHg or DBP 80-89 mmHg)

3-6 g daily— More likely to help when baseline blood pressure is elevated.

High-intensity exercise or repeated-sprint training

6-8 g 30-60 minutes before activity— Acute effects are usually modest; some people respond better after 1-2 weeks of daily use.

GI upset or nausea at doses ≥6 g

1.5-3 g twice daily— Splitting the dose often improves tolerance without changing the daily total.

Safety & Limits

Upper Safe Limit

No official UL; up to 10 g/day has been studied short term in adults with generally good tolerability.

Cycling

Safe for continuous use

Contraindications

Nitrate medications (nitroglycerin, isosorbide) — additive vasodilation may lower blood pressure too much

PDE-5 inhibitors like sildenafil or tadalafil — may further lower blood pressure and increase dizziness

Antihypertensive medication — may potentiate blood-pressure lowering; monitor closely

Chronically low blood pressure — may worsen lightheadedness

Pregnancy or breastfeeding — insufficient safety data

Severe kidney disease — limited human safety data; use only with clinician oversight

Synergies

Beetroot / dietary nitrates

Nitrates raise nitric oxide through the nitrate-nitrite pathway, complementing citrulline's arginine-NOS pathway for blood-flow effects.

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