Nitric Oxide Precursors

L-Citrulline · L-Arginine · Nitrate · Citrulline Malate

Snapshot

Indications	Contraindications
Blood pressure¹ Exercise performance² Erectile dysfunction³ Preeclampsia prevention⁴ Cardiometabolic health⁵	Hypotension⁶ Under 18 years⁶

Nitric oxide precursors are L-arginine, L-citrulline (including citrulline malate), and inorganic nitrate, which raise nitric oxide, a vasodilator, through nitric oxide synthase or the nitrate-nitrite pathway⁷. L-arginine is used for erectile function and in pregnancy for preeclampsia, and citrulline for cardiometabolic health.

Citrulline malate showed no overall effect on strength in resistance-trained adults, and potassium nitrate did not improve exercise capacity in heart failure with preserved ejection fraction. In 2022, a randomized trial in obese older adults found that adding citrulline to interval training increased muscle strength and reduced fat mass⁸. Many products list nitric oxide precursors, as capsules, liquids, and powders; see Form comparison.

Because all three ingredients lower vascular tone, United States product labels warn that combining them with organic nitrate medications or blood pressure medications may cause an unsafe drop in blood pressure⁶. Per 14 of 30 United States product labels, patients taking antihypertensives are told to consult a healthcare practitioner⁶.

Last updated October 15, 2026. Read how we make monographs.

In the full monograph

97 sources, 90 studies

When to useThe situations practitioners use it for, each with the reason and the study behind it.
SafetyWho should avoid it, who needs extra care, and the side effects reported in studies.
InteractionsThe medicines and supplements it interacts with, the effect of each, and what labeling says to watch.
Protocol notesThe doses used in studies, how and when they were taken, and how the forms on the market compare.
How it worksWhat it is and how it works in the body, in plain terms.
Published studiesThe studies behind each use, popular claims checked against them, and trials still under way.
Word of mouthWhat patients and practitioners report online, kept separate from the clinical evidence.
Clinical perspectiveA closing read of where the evidence is solid, where it is thin, and what has not been studied.

Snapshot

In the full monograph

Sources