NOW Foods Arginine & Ornithine 500 / 250 mg: Targeted Nitric Oxide & Urea Cycle Support
A scientifically balanced 2:1 ratio of two free-form amino acids crafted to fuel muscle blood flow, speed up workout recovery, and clear cellular waste.
When training hard or pushing physical limits, muscles demand two critical things: continuous oxygen and nutrient delivery during exercise, followed by rapid removal of metabolic waste afterward. NOW Foods Arginine & Ornithine 500 / 250 mg delivers this dual-action support by uniting two biologically complementary amino acids in one daily formula.
Quick Formula Snapshot:
Active Potency: 1,000 mg L-Arginine and 500 mg L-Ornithine per 2-capsule serving (500 mg Arginine / 250 mg Ornithine per single capsule).
Free-Form Bioavailability: Rapidly absorbed without requiring enzymatic breakdown from dietary whole proteins.
Core Applications: Vascular pumps, endothelial nitric oxide synthesis, hepatic ammonia detoxification, and nighttime protein recovery.
How Arginine and Ornithine Work Together: The Plain-English Science
While many sports supplements focus solely on temporary pre-workout stimulation, L-Arginine and L-Ornithine act as foundational metabolic catalysts. They work in tandem across two essential biochemical pathways:
1. Nitric Oxide Production and Muscle Vascularity
L-Arginine is the body's exclusive direct dietary precursor to nitric oxide (NO), a microscopic signaling gas produced by the inner lining of blood vessels (vascular endothelium). Nitric oxide signals smooth muscle walls to relax and widen—a biological process known as vasodilation.
Widening these vascular channels works like turning a single-lane road into an open highway: blood, oxygen, glucose, and branched-chain amino acids surge directly into working muscle fibers during high-intensity exercise. This creates fuller muscle pumps, improves muscular stamina, and reduces immediate muscle fatigue during heavy lifting or cardio sessions.
Scientific Validation: Palmer RM, Ashton DS, Moncada S. Vascular endothelial cells synthesize nitric oxide from L-arginine. Nature. 1988;333(6174):664-666; Böger RH. The pharmacodynamics of L-arginine. The Journal of Nutrition. 2007;137(6 Suppl 2):1650S-1655S.
2. The Urea Cycle: Clearing Toxic Ammonia
During strenuous exercise or high-protein metabolism, the body breaks down nitrogen-rich amino acids, creating a natural byproduct called ammonia. Ammonia is a metabolic waste compound that accumulates in muscle tissue and the bloodstream, impairing neuromuscular signaling and causing sudden muscular burn and exhaustion.
This is where L-Ornithine provides immense value. In the liver's urea cycle (the body's internal filtration system), Ornithine acts as an essential catalyst that binds free ammonia and converts it into neutral urea, which the kidneys safely filter and flush out in urine. Supplementing with L-Ornithine alongside L-Arginine supports this natural cleansing pathway, helping preserve energy output and protect muscles from premature exhaustion.
Scientific Validation: Sugino T, Shirai T, Kajimoto Y, Kajimoto O. L-ornithine supplementation attenuates physical fatigue in healthy volunteers by promoting lipid metabolism and activating the urea cycle. Nutrition Research. 2008;28(11):738-743; Morris SM Jr. Enzymes of arginine metabolism. The Journal of Nutrition. 2004;134(10 Suppl):2743S-2747S.
3. Exercise Recovery and Growth Hormone Secretion
Clinical research demonstrates that combining oral L-Arginine with L-Ornithine stimulates anterior pituitary signaling, suppressing somatostatin (a growth hormone inhibitor) and supporting higher circulating serum levels of growth hormone (GH) and Insulin-Like Growth Factor 1 (IGF-1) following heavy resistance training.
Scientific Validation: Zajac A, Poprzęcki S, Zebrowska A, Chalimoniuk M, Langfort J. Arginine and ornithine supplementation increases growth hormone and insulin-like growth factor-1 serum levels after heavy-resistance exercise in strength-trained athletes. The Journal of Strength and Conditioning Research. 2010;24(4):1082-1090.
Every batch of NOW Foods Arginine & Ornithine (Item # N0040 / NOW-00040) is formulated with pharmaceutical-grade, pure free-form amino acids for reliable dissolution and bioavailability.
Supplement Facts
Serving Size: 2 Veg Capsules
Servings Per Container: 50 (100 Count) or 125 (250 Count)
Active Ingredient
Amount Per Serving (% Daily Value)
L-Arginine (Free-Form)
1 g (1,000 mg) *
L-Ornithine (from 644 mg L-Ornithine HCl)
500 mg *
* Daily Value (DV) not established.
Ingredient Transparency
Other Ingredients: Hypromellose (cellulose capsule) and Stearic Acid (vegetable source).
Allergen Free From: Not manufactured with wheat, gluten, soy, milk, egg, fish, shellfish, tree nut, or sesame ingredients.
NOW Brand Quality Assurance: ISO 17025 Labs & Contaminant Screening
In an unregulated online marketplace flooded with white-labeled supplements that under-deliver on active potency or conceal heavy metal contaminants, NOW Foods maintains one of the most advanced quality assurance operations in North America.
Before a single bottle of NOW Arginine & Ornithine leaves their facility, it passes an exhaustive array of analytical testing protocols:
NOW operates world-class in-house analytical testing laboratories run by more than 150 chemists, microbiologists, and research scientists. The team executes more than 31,000 analytical tests every month, guaranteeing that what is printed on the label matches the exact contents of every capsule.
✓ Strict Heavy Metal Screening via ICP-MS
Using state-of-the-art Inductively Coupled Plasma Mass Spectrometry (ICP-MS), NOW tests both raw materials and finished goods for trace heavy metals—detecting contaminants down to parts per billion (ppb). Finished products must meet internal thresholds that routinely exceed the United States Pharmacopeia (USP) guidelines and adhere strictly to California Proposition 65 limits for lead, arsenic, cadmium, and mercury.
✓ Potency & Compound Verification (HPLC / UPLC)
High-Performance Liquid Chromatography (HPLC) and Ultra-Performance Liquid Chromatography (UPLC) inspect the molecular integrity of the raw L-Arginine and L-Ornithine HCl. This eliminates degraded or bound amino acids, verifying complete free-form purity and rapid gastrointestinal dissolution.
✓ Microbiological Purity & Allergen Control
Batches are screened for harmful environmental pathogens—including Salmonella, E. coli, Staphylococcus aureus, yeast, and molds. Manufactured under strict Current Good Manufacturing Practice (cGMP) regulations audited under 21 CFR Part 111, the facility avoids cross-contamination with common dietary allergens.
How to Take Arginine & Ornithine: Optimal Timing & Real-World Usage
To experience the full vascular and recovery benefits of this formula, proper timing and digestive conditions are essential.
The Empty-Stomach Rule
Always consume capsules with at least 8 to 10 ounces of water or fruit juice on an empty stomach (at least 45 to 60 minutes before a meal, or 2 hours after). Free-form amino acids utilize competitive peptide transporters along the intestinal wall. If taken alongside dietary protein (such as meat, eggs, or a whey protein shake), L-Arginine and L-Ornithine must compete against millions of other amino acids, significantly dulling their targeted benefits. Taking them with water or juice ensures fast, unobstructed uptake.
Choose Your Timing Strategy Based on Your Goals:
Strategy A: Pre-Workout (For Muscle Pumps & Blood Flow): Take 2 capsules 30 to 45 minutes before strength training or athletic competition. This gives the body sufficient time to metabolize L-Arginine into nitric oxide, promoting vascular vasodilation during peak physical effort.
Strategy B: Bedtime (For Overnight Recovery & Urea Clearance): Take 2 capsules 30 minutes before sleep on an empty stomach. Growth hormone naturally surges during early stages of slow-wave sleep; taking this amino acid combination at night supports pituitary function and promotes overnight tissue repair while clearing accumulated metabolic ammonia.
Essential Health Warnings: Who Should NOT Take This Formula
Dietary supplements directly affect human biochemistry. To ensure personal safety, please review these medical contraindications prior to supplementation:
Do not use this product if you have a history of a heart attack or established coronary artery disease. In a landmark clinical trial (the VINTAGE MI study published in JAMA), post-myocardial infarction patients supplementing with L-arginine did not experience improved vascular stiffness and showed unfavorable clinical outcomes. If you have active cardiovascular disease, consult your cardiologist before using any amino acid product. Reference: Schulman SP, et al. L-arginine therapy in acute myocardial infarction: the VINTAGE MI randomized clinical trial. JAMA. 2006;295(1):58-64.
Herpes Simplex Virus (Cold Sores / HSV-1 & HSV-2)
The Herpes simplex virus requires the amino acid arginine to replicate within host cells. Elevating arginine levels without balancing dietary lysine may trigger cold sore outbreaks or genital flare-ups in susceptible individuals. If you are prone to cold sores, consult your healthcare provider or balance your intake with L-Lysine. Reference: Griffith RS, et al. Success of L-lysine therapy in frequently recurrent herpes simplex infection. Dermatologica. 1987;175(4):183-190.
Blood Pressure Medications, Glaucoma & Upcoming Surgery
Because L-Arginine triggers natural vasodilation, it can lower systemic blood pressure. If you are taking antihypertensive drugs, nitrates, or medications for erectile dysfunction (PDE5 inhibitors), combining them with arginine may cause blood pressure to drop excessively (hypotension). Individuals with glaucoma, asthma, renal disease, or those scheduled for surgery within two weeks should consult their physician before use. Not intended for pregnant or nursing women. Keep out of reach of children.
Why Choose VitaNet, LLC for Your Sports Nutrition Needs?
Purchasing vitamins online shouldn't involve guessing whether a marketplace third-party reseller stored your supplements in an unheated garage or hot warehouse[cite: 1]. At VitaNet, LLC, natural wellness has been our sole focus for decades[cite: 1]:
✓ Family-Owned Independent Heritage Since 1995[cite: 1]
Founded in 1995 and operating from our physical headquarters in Hartville, Ohio, VitaNet brings over 31 years of direct nutritional expertise and retail integrity to every customer order[cite: 1].
✓ Better Business Bureau A+ Accreditation[cite: 1]
We hold an A+ rating with the Better Business Bureau, reflecting over three decades of straightforward, transparent, and responsive customer service[cite: 1].
We believe in complete customer peace of mind[cite: 1]. If you are dissatisfied with any product for any reason, we offer an unconditional 100% money-back guarantee—and we even cover return shipping costs, even on opened bottles[cite: 1].
✓ Climate-Controlled Storage & Direct Manufacturer Sourcing[cite: 1]
Every bottle of NOW Sports Arginine & Ornithine is sourced directly from certified manufacturing lines and kept in strict temperature-controlled storage to maintain optimal potency and freshness[cite: 1].
Frequently Asked Questions (FAQ)
What is the specific benefit of combining Arginine with Ornithine in a 2:1 ratio?
L-Arginine acts as a direct nitric oxide precursor to expand blood vessels, while L-Ornithine acts as a catalyst in the liver's urea cycle to eliminate ammonia buildup. Because ornithine is synthesized from arginine inside the body, supplementing them together in a 2:1 ratio (1,000 mg to 500 mg) ensures immediate nitric oxide release while sparing your arginine reserves for ongoing protein synthesis and cellular repair.
Why must I take Arginine & Ornithine on an empty stomach?
Amino acids share the same intestinal transporter pathways. When ingested with whole foods or protein shakes, the free-form amino acids compete with thousands of other peptide fragments, drastically reducing their absorption rate. Consuming them with water or juice on an empty stomach allows them to quickly pass into the bloodstream for maximum effectiveness.
Should I take this supplement before working out or before going to bed?
Both methods are clinically viable depending on your primary training goal. Take 2 capsules 30 to 45 minutes prior to exercise if your main objective is improved muscular pump, stamina, and vascular nutrient delivery. Take 2 capsules before bed on an empty stomach if your primary objective is nighttime growth hormone release, muscle repair, and morning recovery.
How does NOW Foods guarantee that this product is free from heavy metal contamination?
NOW Foods tests every batch in their in-house ISO/IEC 17025:2017 accredited analytical laboratory. Using Inductively Coupled Plasma Mass Spectrometry (ICP-MS), technicians analyze raw materials and finished products down to parts per billion (ppb) for lead, arsenic, cadmium, and mercury, ensuring every batch complies with strict California Proposition 65 and USP safety standards.
Can I take Arginine & Ornithine if I am prone to cold sores?
Individuals prone to Herpes simplex virus (HSV-1 or HSV-2) outbreaks should exercise caution. Arginine encourages viral replication, while lysine suppresses it. If you choose to supplement with arginine, consider balancing it with an equal or greater amount of L-Lysine, and consult your medical doctor if outbreaks occur.
