Quick answer: L-Arginine and L-Citrulline are complementary amino acids that support nitric oxide production and healthy blood flow. The key difference: L-Citrulline converts into L-Arginine in the body, which helps sustain nitric oxide levels over time. BPI Sports pairs both in one easy capsule — 500 mg L-Arginine and 250 mg L-Citrulline per serving — to support circulation, performance, and muscle function.*
What are L-Arginine and L-Citrulline?
Both are amino acids — building blocks your body uses in countless processes, including muscle function and metabolism.
- L-Arginine is a direct precursor to nitric oxide (NO), a molecule that helps blood vessels relax and widen, supporting healthy blood flow and circulation.*
- L-Citrulline converts into L-Arginine in the body. This "back-door" route helps promote more sustained nitric oxide levels than L-Arginine alone.*
L-Arginine vs L-Citrulline: what's the difference?
They pursue the same goal — supporting nitric oxide and blood flow — by different paths:
| L-Arginine | L-Citrulline | |
|---|---|---|
| Main role | Direct precursor to nitric oxide | Converts into L-Arginine in the body |
| Nitric oxide support | Fast, direct | More sustained over time |
| Per serving (BPI) | 500 mg | 250 mg |
This is why BPI Sports pairs them together in a single capsule instead of asking you to choose — you get both an immediate and a more sustained effect.*
How nitric oxide supports blood flow
Nitric oxide signals the smooth muscle in your blood vessel walls to relax. When vessels widen, blood, oxygen, and nutrients move more freely to working muscles — which is why nitric oxide precursors are a staple in training nutrition.*
Beyond the pump: performance & muscle function
Together, this amino acid complex is designed to support exercise performance, endurance, and muscle function.* In short, it supports:*
- Nitric oxide production for healthy blood flow and circulation*
- Exercise performance and endurance*
- Healthy muscle function*
When and how to take it
BPI Sports L-Arginine + L-Citrulline comes in easy capsules — no mixing, no taste. The suggested use is to take 1 capsule twice daily with 8–12 oz of water. Many active people take a serving before training so nitric oxide support lines up with their workout.
How to choose a nitric oxide supplement
Look for a product that combines both amino acids at meaningful doses, and offers real value (BPI Sports comes in 120 and 240-serving bottles). BPI Sports L-Arginine + L-Citrulline delivers 500 mg L-Arginine and 250 mg L-Citrulline per serving to support nitric oxide, blood flow, and performance.*
Frequently asked questions
Should I take L-Arginine or L-Citrulline?
You don't have to choose. Because L-Citrulline converts into L-Arginine in the body, taking both together supports both an immediate and a more sustained boost in nitric oxide. BPI Sports combines 500 mg L-Arginine and 250 mg L-Citrulline in one capsule.*
What does L-Arginine + L-Citrulline do?
Together they support nitric oxide production for healthy blood flow and circulation, and support exercise performance, endurance, and muscle function.*
How do I take it?
Take 1 capsule twice daily with 8–12 oz of water. Many people take a serving before training so nitric oxide support aligns with their workout.
Is it a stimulant pre-workout?
No. It's a nitric oxide and blood-flow support supplement with no caffeine, so you can stack it with your existing pre-workout or use it on its own.
Is it a powder or capsule?
It's an easy-to-take capsule — no mixing and no taste — with 500 mg L-Arginine and 250 mg L-Citrulline per serving.
Shop L-Arginine + L-Citrulline →
*These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease.