10 Best L-Glutamine Supplements (2026) Reviewed
L-glutamine is the most abundant amino acid in the human body, playing a critical role in muscle recovery, gut health, and immune function. While your body naturally produces glutamine, intense exercise, stress, illness, or injury can deplete your stores faster than they can be replenished—making supplementation a smart choice for athletes, fitness enthusiasts, and anyone focused on digestive wellness.
Finding the right L-glutamine supplement requires navigating a crowded market with varying quality standards, dosages, and formats. Whether you prefer powder for flexible dosing or capsules for convenience, third-party testing and manufacturing standards matter. We researched dozens of products, verified certifications, and analyzed third-party reviews from ConsumerLab, Healthline, and Innerbody to bring you this comprehensive guide.
Our selection includes products from established brands with GMP-certified facilities, NSF Certified for Sport options for competitive athletes, and budget-friendly alternatives that don’t compromise on purity.
Table of Contents
- Quick Comparison Table
- Powder vs. Capsules: Which Form Is Right for You?
- Individual Product Reviews
- L-Glutamine Buying Guide
- How to Take L-Glutamine
- Potential Benefits of L-Glutamine
- Safety Considerations
- Frequently Asked Questions
- Bottom Line Recommendations
Quick Comparison Table
| Product | Form | Serving Size | Key Differentiator | Best For | Winner |
|---|---|---|---|---|---|
| Thorne L-Glutamine Powder | Powder | 5g | NSF Certified for Sport, trusted by 100+ pro teams | Serious athletes & quality-focused buyers | 🏆 TOP PICK |
| Nutricost L-Glutamine Powder | Powder | 5g | Exceptional value, 100 servings per container | Budget-conscious buyers | 🥇 Best Value |
| Pure Encapsulations L-Glutamine 500mg | Capsules | 500mg | Hypoallergenic, no unnecessary additives | Sensitive individuals | 🥇 Best Premium Capsules |
| NOW Foods L-Glutamine Powder | Powder | 5g | GMP certified, family-owned since 1968 | Trusted brand seekers | 🥇 Best Established Brand |
| BulkSupplements L-Glutamine Powder | Powder | 5g | Third-party tested, no fillers | Bulk buyers & supplement stackers | 🥇 Best Bulk Value |
| Optimum Nutrition Glutamine Capsules | Capsules | 1g (2 caps) | Rapid disintegration formula, NSF GMP certified | Gym-goers & bodybuilders | 🥇 Best for Athletes |
| Momentous L-Glutamine Powder | Powder | 5g | NSF Certified for Sport, Huberman-recommended | Competitive & elite athletes | 🥇 Best for Elite Athletes |
| Life Extension L-Glutamine 500mg | Capsules | 500mg | Science-backed formulation, 40+ years expertise | Health-focused adults | 🥇 Best for Immune Support |
| Sports Research L-Glutamine | Powder | 5g | Informed Sport tested, fermented production | Drug-tested athletes | 🥇 Best Informed Sport Certified |
| Nutricost L-Glutamine Capsules | Capsules | 800mg | High-dose capsules, excellent value | Capsule-preferring value seekers | 🥇 Best Value Capsules |
Powder vs. Capsules: Which Form Is Right for You?
Powder Form
Pros: Powder allows for flexible dosing, typically offers better value per gram, and absorbs quickly when mixed with water or added to shakes. Most clinical research uses powder form at higher doses (5-10g), making it easier to replicate studied protocols.
Cons: Requires measuring and mixing, less convenient for travel, and some users may find the slightly chalky texture unappealing.
Best for: Athletes seeking higher doses, those who already use protein shakes, and budget-conscious buyers.
Capsule Form
Pros: Convenient, portable, no taste, precise dosing without measuring, and easy to incorporate into existing supplement routines.
Cons: Typically more expensive per gram, and achieving therapeutic doses (5g+) may require taking multiple capsules.
Best for: Travelers, those sensitive to taste, and people who prefer simple, no-fuss supplementation.
Individual Product Reviews
Thorne L-Glutamine Powder — Best Overall
Thorne’s L-Glutamine Powder stands out as our top pick for its uncompromising quality standards, NSF Certified for Sport certification, and trust from over 100 professional sports teams.
Thorne Research has built its reputation on clinical-grade supplements, and their L-Glutamine Powder exemplifies this commitment. Each 5.6g scoop delivers 5g of pure L-glutamine with absolutely no other ingredients—no fillers, no additives, no excipients. The NSF Certified for Sport designation means this product has been independently tested for banned substances and label accuracy, making it suitable for competitive athletes subject to drug testing.
Thorne partners with Mayo Clinic on wellness research and is the official supplement supplier for numerous professional teams and U.S. National Teams. The company maintains its own manufacturing facilities in Charleston, SC, with four rounds of testing throughout production. While the premium price reflects these quality investments, serious athletes and health-conscious consumers often find the peace of mind worth the cost.
Key Specifications:
- Serving size: 5g (one scoop)
- Servings per container: ~90
- Certifications: NSF Certified for Sport
- Other ingredients: None
- Form: Unflavored powder
Considerations: Premium pricing may not suit budget-conscious buyers. The large container size requires commitment to regular use.
Nutricost L-Glutamine Powder — Best Budget
Nutricost delivers exceptional value without sacrificing quality, offering 100 servings of pure L-glutamine at a fraction of premium brand prices.
For buyers seeking quality L-glutamine without the premium price tag, Nutricost has become a go-to brand. Their unflavored powder provides 5g of L-glutamine per serving with no additives, manufactured in an NSF-certified, GMP-compliant, FDA-registered facility in the USA. Independent testing by ISO-accredited laboratories verifies purity and potency.
Nutricost has earned recognition from third-party review sites including Healthline, which praised their taste and affordability. The product is non-GMO, gluten-free, and suitable for vegans. Available in multiple sizes (250g, 500g, 1kg), Nutricost allows buyers to start small or stock up for long-term use. Flavored versions with stevia sweetening are also available for those who prefer a more palatable option.
Key Specifications:
- Serving size: 5g (one scoop)
- Servings per container: 100 (500g container)
- Certifications: NSF-certified facility, GMP compliant
- Other ingredients: None
- Form: Unflavored powder
Considerations: Not NSF Certified for Sport (individual product), so may not be ideal for drug-tested athletes requiring batch-level testing.
Pure Encapsulations L-Glutamine 500mg — Best Premium Capsules
Pure Encapsulations offers a hypoallergenic formulation free from common allergens and unnecessary additives, ideal for sensitive individuals and those following elimination diets.
Pure Encapsulations has built a loyal following among healthcare practitioners and patients with sensitivities by creating supplements without unnecessary excipients. Their L-Glutamine capsules contain only free-form L-glutamine, ascorbyl palmitate (a vitamin C derivative for stability), and a vegetarian capsule—nothing else. The product is free from wheat, eggs, tree nuts, peanuts, gluten, artificial colors, flavors, sweeteners, coatings, GMOs, and unnecessary binders.
Manufactured in their Massachusetts facility, Pure Encapsulations maintains rigorous quality control with independent potency and purity testing. The company’s commitment to hypoallergenic formulations has made them a trusted choice for integrative medicine practitioners. The 500mg per capsule dosage allows flexible dosing (1-3 capsules daily between meals), though reaching therapeutic doses requires multiple capsules.
Key Specifications:
- Serving size: 500mg (1 capsule)
- Servings per container: 90
- Certifications: Certified Gluten-Free
- Other ingredients: Ascorbyl palmitate, vegetarian capsule (cellulose, water)
- Form: Vegetarian capsules
Considerations: Higher cost per gram compared to powder forms. Reaching 5g dose requires 10 capsules, making powder more practical for high-dose protocols.
NOW Foods L-Glutamine Powder — Best Established Brand
NOW Foods combines over 55 years of supplement manufacturing experience with NPA A-rated GMP certification, delivering reliable quality at accessible prices.
As a family-owned company since 1968, NOW Foods has earned its reputation as a trusted name in affordable, quality supplements. Their L-Glutamine Powder is pure free-form glutamine of the highest grade available, with no additional ingredients. Every aspect of NOW’s manufacturing process is GMP-certified, including laboratory testing methods for stability, potency, and product formulation.
ConsumerLab included NOW’s L-Glutamine products in their testing and the brand consistently meets quality standards. The product is not manufactured with common allergens including wheat, gluten, soy, milk, egg, fish, shellfish, or tree nuts. NOW offers multiple sizes and formats (powder and capsules), giving consumers flexibility based on their preferences and budget.
Key Specifications:
- Serving size: 5g (1 rounded teaspoon)
- Servings per container: ~34 (1 lb container)
- Certifications: NPA A-rated GMP, Halal, Kosher
- Other ingredients: None
- Form: Unflavored powder
Considerations: Container size is smaller than some competitors, potentially requiring more frequent reorders for regular users.
BulkSupplements L-Glutamine Powder — Best Bulk Value
BulkSupplements specializes in pure, single-ingredient supplements at wholesale prices, making it the ideal choice for those who prefer to buy in bulk or create custom supplement stacks.
True to their name, BulkSupplements focuses on providing pure ingredients without fillers, flavors, or additives. Their L-Glutamine powder undergoes rigorous third-party testing for purity and potency, with products manufactured in cGMP-compliant facilities. The unflavored formula mixes easily with water, juice, or protein shakes, making it versatile for various supplementation needs.
BulkSupplements offers their L-glutamine in multiple sizes from 500g to 1kg, providing excellent value for committed users. The resealable bag packaging is less premium than bottles but keeps costs down and is space-efficient. ConsumerLab included BulkSupplements in their L-glutamine testing lineup, and the brand has earned a solid reputation among fitness enthusiasts who prioritize pure ingredients and value.
Key Specifications:
- Serving size: 5g (2 teaspoons)
- Servings per container: 100 (500g bag)
- Certifications: cGMP compliant, third-party tested
- Other ingredients: None
- Form: Unflavored powder in resealable bag
Considerations: Bag packaging is less convenient than containers with scoops. Not NSF Certified for Sport.
Optimum Nutrition L-Glutamine Capsules — Best for Athletes
Optimum Nutrition’s Glutamine Capsules deliver convenient, rapid-disintegration dosing from a brand that has been a staple in gyms worldwide for over 35 years.
Optimum Nutrition (ON) is one of the most recognized names in sports nutrition, trusted by athletes in over 90 countries. Their Glutamine Capsules are formulated for rapid disintegration and maximum absorption, with each capsule providing 500mg of pure L-glutamine. The recommended serving of 2 capsules delivers 1g—ideal for those who prefer incremental dosing throughout the day.
ON’s in-house manufacturing is NSF International GMP registered, with Certificate of Analysis verification for all raw materials and independent laboratory testing. The company implements HACCP protocols and conducts routine quality checks throughout production. For bodybuilders and gym-goers who want a no-fuss way to add glutamine to their post-workout routine, these capsules integrate seamlessly with other ON products like Gold Standard Whey.
Key Specifications:
- Serving size: 1g (2 capsules)
- Servings per container: 120 (240 capsules)
- Certifications: NSF GMP registered
- Other ingredients: Gelatin, magnesium stearate
- Form: Gelatin capsules
Considerations: Contains gelatin (not vegetarian). Reaching 5g dose requires 10 capsules. Cost per gram is higher than powder options.
Momentous L-Glutamine Powder — Best for Elite Athletes
Momentous brings elite-level quality standards with NSF Certified for Sport testing, Department of Defense research partnerships, and endorsement from neuroscientist Andrew Huberman.
Momentous has rapidly become the supplement brand of choice for professional sports teams, with 100% of NFL teams now using their products. Their L-Glutamine powder is NSF Certified for Sport, meaning each batch is tested for over 270 banned substances and verified for label accuracy. The company has received 11 innovation and research contracts from the U.S. Department of Defense to advance human performance.
Dr. Andrew Huberman, the Stanford neuroscientist behind the popular Huberman Lab podcast, has featured Momentous products in his protocols. Each serving delivers 5g of pure, plant-derived L-glutamine that’s vegan-friendly and dissolves easily without taste or grit. While the price point is premium, athletes subject to drug testing and those who prioritize science-backed formulations often find Momentous worth the investment.
Key Specifications:
- Serving size: 5g (one scoop)
- Servings per container: 60
- Certifications: NSF Certified for Sport
- Other ingredients: None
- Form: Unflavored powder, vegan
Considerations: Premium pricing. Smaller serving count than some competitors. May be out of stock due to popularity.
Life Extension L-Glutamine — Best for Immune Support
Life Extension leverages over 40 years of science-backed supplement development to deliver a glutamine formula designed for immune function, gut health, and active lifestyles.
Life Extension has spent four decades funding anti-aging research and developing evidence-based supplements. Their L-Glutamine capsules provide 500mg per serving in a vegetarian formula free from gluten and GMOs. The company emphasizes glutamine’s role as fuel for immune cells and cells lining the digestive tract, making this product particularly relevant for those focused on immune resilience.
Life Extension maintains rigorous quality standards with 99% of products manufactured in the USA. Their formulations are guided by published scientific research, and the company provides certificates of analysis for all products. For health-conscious adults who want a reputable brand with a science-first approach—rather than a sports-focused formulation—Life Extension offers a trustworthy option.
Key Specifications:
- Serving size: 500mg (1 capsule)
- Servings per container: 100
- Certifications: 99% manufactured in USA
- Other ingredients: Vegetable cellulose, microcrystalline cellulose, rice flour, stearic acid
- Form: Vegetarian capsules
Considerations: Lower dose per capsule requires multiple capsules for therapeutic amounts. Contains some common excipients.
Sports Research L-Glutamine — Best Informed Sport Certified
Sports Research combines a proprietary 5-step fermentation process with Informed Sport certification, providing drug-tested athletes with confidence in every scoop.
Founded in Southern California in 1980, Sports Research is a family-owned company that has evolved into a trusted name in quality supplements. Their L-Glutamine is produced using a proprietary 5-step purification process, resulting in a fine powder that mixes smoothly without clumping. The product carries Informed Sport certification—a global testing program that verifies supplements for prohibited substances.
Sports Research sources their L-glutamine from a single trusted supplier, ensuring consistency across batches. The formula is entirely vegan, non-GMO tested (IGEN verified), and NSF gluten-free certified. For athletes who compete in drug-tested sports but want an alternative to NSF Certified for Sport products, Informed Sport testing provides similar assurance at a competitive price point.
Key Specifications:
- Serving size: 5g (one scoop)
- Servings per container: 60 (10.58 oz container)
- Certifications: Informed Sport, IGEN Non-GMO, NSF Gluten-Free
- Other ingredients: None
- Form: Unflavored powder, vegan
Considerations: Slightly smaller serving count than some competitors. Available in limited container sizes.
Nutricost L-Glutamine Capsules — Best Value Capsules
Nutricost extends their value proposition to capsule form, delivering 800mg of L-glutamine per capsule at an accessible price point.
For those who prefer capsules but don’t want to pay premium prices, Nutricost’s L-Glutamine Capsules offer an excellent middle ground. Each capsule provides 800mg of L-glutamine—higher than the 500mg commonly found in competing products—meaning fewer capsules are needed to reach therapeutic doses. The 180-capsule bottle provides excellent value for regular users.
Like Nutricost’s powder, these capsules are manufactured in an NSF-certified, GMP-compliant, FDA-registered facility. The formula is non-GMO and gluten-free, suitable for various dietary needs. While not reaching the purity standards of hypoallergenic brands like Pure Encapsulations, Nutricost delivers solid quality for mainstream consumers seeking capsule convenience at budget-friendly prices.
Key Specifications:
- Serving size: 800mg (1 capsule)
- Servings per container: 180
- Certifications: NSF-certified facility, GMP compliant
- Other ingredients: Vegetable cellulose (capsule)
- Form: Vegetarian capsules
Considerations: Still requires 6+ capsules to reach 5g dose. Not third-party tested at the individual product level for banned substances.
L-Glutamine Buying Guide
Key Quality Indicators
Third-Party Testing: Look for products tested by independent laboratories for purity, potency, and contaminants. NSF Certified for Sport and Informed Sport certifications are gold standards for athletes, while USP verification and ConsumerLab approval provide assurance for general consumers.
Manufacturing Standards: GMP (Good Manufacturing Practice) certification indicates the facility follows FDA-established quality guidelines. Look for products manufactured in FDA-registered facilities with documented testing protocols.
Ingredient Transparency: The best L-glutamine supplements contain only L-glutamine (or minimal stabilizers for capsules). Avoid products with long ingredient lists, artificial flavors, or unnecessary fillers.
Free-Form L-Glutamine: Virtually all quality L-glutamine supplements use the free-form version, which is readily absorbed. Don’t pay extra for products marketing “free-form” as a premium feature—it’s the standard.
Certifications That Matter
NSF Certified for Sport: Batch-level testing for banned substances, label accuracy, and contaminants. Required by many professional sports leagues.
Informed Sport: Similar to NSF, tests for prohibited substances. Recognized by many international sporting bodies.
GMP Certified: Facility meets FDA manufacturing standards. Look for NPA A-rated GMP or NSF GMP registration.
Non-GMO Project Verified: Independent verification that the product doesn’t contain genetically modified ingredients.
Red Flags to Avoid
- Products with proprietary blends that hide actual glutamine amounts
- Extreme discount pricing that seems too good to be true
- No information about manufacturing location or quality testing
- Excessive additives, artificial colors, or sweeteners
- Health claims that sound too dramatic (glutamine supports wellness but doesn’t cure diseases)
How to Take L-Glutamine
Recommended Dosage
Most research uses doses between 5-10g daily. For general wellness and gut health support, 5g (approximately one teaspoon of powder or the equivalent in capsules) once daily is a common starting point. Athletes involved in intense training may benefit from higher doses, sometimes up to 20-30g daily divided across multiple servings, though such protocols should ideally be supervised by a healthcare professional.
Best Time to Take
For muscle recovery: Post-workout is ideal, as glutamine levels deplete during intense exercise. Adding L-glutamine to your post-workout protein shake is a convenient approach.
For gut health: Take on an empty stomach, typically first thing in the morning or between meals, to maximize absorption by intestinal cells.
For immune support: Consistency matters more than timing. Taking glutamine at the same time daily helps maintain steady levels.
Usage Tips by Form
Powder: Mix with 8-12 oz of water, juice, or add to protein shakes. Most powders are unflavored and dissolve reasonably well, though slight grittiness is normal. Some users prefer flavored versions sweetened with stevia.
Capsules: Take with water, ideally between meals for gut health or with your post-workout meal for muscle recovery. If taking multiple capsules, you can split them throughout the day.
Duration and Cycling
L-glutamine may be taken continuously without the need for cycling. Unlike some supplements, there’s no evidence of tolerance buildup or diminishing returns with extended use. However, periodic reassessment with a healthcare provider is wise, especially if taking higher doses or using glutamine for specific health conditions.
Potential Benefits of L-Glutamine
Muscle Recovery Support
Research suggests L-glutamine supplementation may help reduce muscle soreness and support recovery after intense exercise. A 2015 study found that participants taking L-glutamine experienced faster recovery of peak muscle torque following eccentric exercise. A 2024 study on combat-sport athletes found that L-glutamine supplementation after intensive training improved testosterone-to-cortisol ratios and reduced upper respiratory tract infections.
Gut Health
L-glutamine serves as a primary fuel source for cells lining the intestinal tract. Clinical studies suggest glutamine supplementation may help maintain intestinal barrier integrity and support gut lining health. A 2021 study found that L-glutamine, combined with a low FODMAP diet, may help manage IBS symptoms. Research continues to explore glutamine’s role in conditions affecting intestinal permeability.
Immune Function
Glutamine is a critical fuel for immune cells including lymphocytes and macrophages. During periods of intense physical stress, glutamine levels may become depleted, potentially affecting immune function. Supplementation may help maintain glutamine availability for immune cells during demanding training periods or illness recovery.
Metabolic Support
Glutamine plays roles in nitrogen transport, protein synthesis, and glycogen storage. While direct weight loss benefits aren’t well-established, some research suggests glutamine may support healthy metabolic function and help maintain lean muscle mass during caloric restriction.
Safety Considerations
Potential Side Effects
L-glutamine is generally well-tolerated at recommended doses (up to 40g daily for short periods in clinical settings). Mild side effects may include bloating, nausea, dizziness, heartburn, or stomach discomfort. These effects are typically dose-dependent and may be minimized by starting with lower doses and increasing gradually.
Who Should Avoid L-Glutamine
- Individuals with liver disease: Glutamine metabolism may be impaired, potentially affecting ammonia processing
- Individuals with kidney disease: May affect nitrogen balance and waste processing
- Those with Reye’s syndrome: Glutamine supplementation is contraindicated
- People with bipolar disorder: Some concerns exist about glutamine’s potential to affect mood stability
- MSG sensitivity: Some individuals may react to glutamine due to its relationship to glutamate
Drug Interactions
L-glutamine may interact with anti-epilepsy medications and certain chemotherapy drugs. Those taking lactulose for hepatic encephalopathy should avoid glutamine. Always consult a healthcare provider before starting glutamine if you take prescription medications.
When to Consult a Healthcare Provider
- Before starting any new supplement, especially with existing health conditions
- If pregnant or breastfeeding
- Before surgery (some practitioners recommend stopping supplements beforehand)
- If you experience persistent side effects
- If taking medications with potential interactions
Frequently Asked Questions
What’s the difference between L-glutamine and glutamine?
L-glutamine is the biologically active form of glutamine that your body can readily use. When supplements say “glutamine,” they typically mean L-glutamine. D-glutamine exists but isn’t used by the body in the same way and isn’t found in supplements.
Can I take L-glutamine every day?
Yes, L-glutamine may be taken daily. Unlike some supplements, there’s no evidence that daily use leads to tolerance or diminishing effects. Many people take 5g daily as part of their regular routine.
Should I take L-glutamine with food or on an empty stomach?
For gut health benefits, taking L-glutamine on an empty stomach may maximize absorption by intestinal cells. For muscle recovery, taking it with or after meals (particularly post-workout with protein) works well. Consistency matters more than perfect timing.
Is L-glutamine safe for vegetarians and vegans?
Yes, most L-glutamine supplements are produced through fermentation and are plant-derived. Check labels to confirm—powder forms are typically vegan, while some capsules may contain gelatin.
How long does it take to notice effects from L-glutamine?
Some users report improvements in muscle recovery or gut health within 2-4 weeks of consistent use. Individual results vary based on factors including baseline glutamine status, dosage, and overall diet.
Can L-glutamine help with leaky gut?
Research suggests L-glutamine may support intestinal barrier integrity. It’s commonly recommended as part of gut-healing protocols by integrative medicine practitioners. However, “leaky gut” treatment should be supervised by a healthcare provider who can address underlying causes.
Is L-glutamine the same as glutathione?
No, these are different compounds. Glutathione is an antioxidant that protects cells from damage. L-glutamine is an amino acid involved in muscle recovery, gut health, and immune function. They serve different purposes in the body.
Does L-glutamine help with sugar cravings?
Some practitioners suggest glutamine may help reduce sugar cravings, possibly by providing an alternative fuel for the brain. Scientific evidence for this specific benefit is limited, but anecdotal reports are common.
Should athletes use NSF Certified for Sport L-glutamine?
If you’re subject to drug testing in competitive sports, NSF Certified for Sport or Informed Sport certification provides assurance that the product has been batch-tested for banned substances. This reduces the risk of inadvertent positive tests from contaminated supplements.
Can I take L-glutamine with other supplements?
L-glutamine is commonly combined with protein powders, BCAAs, creatine, and other sports nutrition supplements without issues. It’s also used alongside gut-health supplements like probiotics and digestive enzymes.
Bottom Line Recommendations
For most people seeking quality L-glutamine: Thorne L-Glutamine Powder delivers NSF Certified for Sport quality with a clean, single-ingredient formula trusted by professional athletes and healthcare practitioners alike.
For budget-conscious buyers: Nutricost L-Glutamine Powder provides excellent value with 100 servings of pure L-glutamine from a GMP-certified facility, without compromising on essential quality standards.
For those who prefer capsules: Pure Encapsulations L-Glutamine offers a hypoallergenic formulation for sensitive individuals, while Nutricost L-Glutamine Capsules provides the best value in capsule form.
For competitive athletes requiring drug-tested products: Momentous L-Glutamine (NSF Certified for Sport) or Sports Research L-Glutamine (Informed Sport) provide the third-party testing assurances necessary for professional competition.
For gut health focus: Any of our top picks will support gut health goals, but Life Extension L-Glutamine comes from a brand with particular expertise in health-focused (versus sports-focused) supplementation.
