Best L-Citrulline Supplements for Running & Cycling 2026

Key Takeaways for Endurance Athletes

1. L-Citrulline converts to L-Arginine in the kidneys, which boosts nitric oxide, improves blood flow, supports oxygen delivery, and reduces fatigue in endurance sports.
2. L-Citrulline outperforms L-Arginine, reaching 1.6 to 2 times higher bloodstream levels and improving blood flow by 30 to 50 percent, enabling about 12 percent longer cycling before exhaustion.
3. Citrulline Malate 2:1 works well for sustained ATP production through its malic acid content, while pure L-Citrulline fits precise dosing and stacking needs.
4. Most athletes perform best with 6 to 8 grams of Citrulline Malate or 4 to 6 grams of pure L-Citrulline taken 60 minutes before exercise, with daily use for more than 7 days providing the strongest benefits.
5. Bucked Up’s top-ranked L-Citrulline Powder delivers pure, stackable 3 gram plus dosing for runners and cyclists, so grab a tub and start building peak endurance performance.

How L-Citrulline Supports Real-World Endurance Gains

L-Citrulline improves endurance by targeting three key physiological limits that runners and cyclists face during long efforts. The amino acid bypasses the liver and converts to L-Arginine in the kidneys, which supplies nitric oxide synthase with steady substrate. This conversion increases nitric oxide, widens blood vessels, and improves oxygen and nutrient delivery to working muscles.

L-Citrulline also buffers ammonia, which helps delay fatigue during hard training and racing. Clinical evidence shows a 40 percent reduction in muscle soreness and faster recovery with L-Citrulline supplementation, and research reports that L-Citrulline users lasted 12 percent longer before fatigue than L-Arginine users in endurance tests. The malate in Citrulline Malate supports the Krebs cycle and ATP production, which benefits long, steady aerobic sessions.

Recent studies back these effects across different endurance sports. A 2016 trial using 2.4 grams daily for 7 days cut 4 kilometer cycling time trial completion time by 1.5 percent, and other studies show 12 to 15 percent increases in workout volume with lower perceived exertion. These measurable changes translate into faster race times and more productive training blocks for serious endurance athletes.

Choosing Between Pure L-Citrulline and Citrulline Malate 2:1

Endurance goals and training style determine whether Pure L-Citrulline or Citrulline Malate 2:1 fits better. Citrulline Malate delivers about 1.76 grams of L-Citrulline per 3 gram serving, with the remaining weight as malic acid that supports aerobic energy production through the Krebs cycle. This profile suits athletes who need sustained ATP output during long runs, rides, or races.

Pure L-Citrulline contains only the active amino acid, which helps athletes who want precise control over dose or who stack multiple performance ingredients. Research suggests that increasing L-Citrulline may reduce arterial stiffness more effectively than L-Arginine supplementation, which supports cardiovascular function during long efforts.

Most runners and cyclists do well with 6 to 8 grams of Citrulline Malate 2:1, which balances nitric oxide production and lactic acid buffering. This range supplies roughly 4 to 5.3 grams of L-Citrulline while also providing malic acid for aerobic metabolism. Athletes who want maximum pump and blood flow often choose 4 to 6 grams of Pure L-Citrulline and stack it with ingredients like Nitrosigine or Astragin to support absorption.

Top 7 L-Citrulline Supplements for Endurance in 2026

#1 Bucked Up L-Citrulline Powder delivers pure, unflavored L-Citrulline at 3 grams per scoop, which makes it easy to customize dosing and stacking for nitric oxide and endurance. Athletes can scale up to clinical ranges while keeping full control over their formula. The main advantages include flexibility, ingredient purity, and strong pump support.

#2 Bucked Up Pre-Workout supplies a clinical 6 grams of Citrulline Malate 2:1 with Astragin to support absorption. The formula also includes 200 milligrams of caffeine and beta-alanine, which work together to support endurance without the harsh crash of heavy stimulant products. Transparent labeling, proven endurance support, and solid flavors stand out, while stimulant-sensitive athletes simply need to account for the moderate caffeine dose.

#3 Mother Bucker focuses on advanced pump support with 4 grams of Pure L-Citrulline plus Nitrosigine and Hydroprime Glycerol. This blend targets several vasodilation pathways and supports intramuscular hydration for longer, harder sessions. The 400 milligram caffeine content fits high-tolerance athletes who want intense pre-workout stimulation, and most users take it about 60 minutes before training.

#4 Kaged Pre-Kaged Elite offers a large 10 gram Pure L-Citrulline dose but does not include absorption enhancers. Experienced users may appreciate the high amount, yet the lack of Astragin or similar compounds can limit how much the body actually uses compared with slightly lower but better-supported doses.

Lower-ranked products often fall short through underdosing, weaker absorption, or limited endurance-focused research. Budget options such as PureBulk supply basic L-Citrulline but skip performance stacks, while many mid-tier formulas hide true amounts behind proprietary blends.

Bucked Up L-Citrulline Powder (300g) gives endurance athletes pure L-Citrulline and flexible dosing so they can dial in performance.

Practical L-Citrulline Guidance for Runners and Cyclists

Should Runners Take L-Citrulline?

Most runners gain clear benefits from L-Citrulline because it improves oxygen delivery and helps reduce muscle fatigue during long efforts. Research shows L-Citrulline improves physical performance for cyclists, reduces fatigue, and supports concentration after exercise. Its ammonia-buffering effect becomes especially useful during marathon training and racing, when metabolic waste builds quickly.

Best L-Citrulline Dose for Cycling

Cyclists usually respond best to 6 to 8 grams of Citrulline Malate or 4 to 6 grams of Pure L-Citrulline taken about 60 minutes before riding. Studies show significant time to exhaustion increases with 6 grams daily for 7 days in moderate-intensity cycling, which supports this range as a minimum effective dose.

Does L-Citrulline Increase VO2 Max?

L-Citrulline can support VO2 max improvements by increasing nitric oxide activity, which widens blood vessels and improves blood flow and nutrient delivery. This vasodilation effect directly supports higher oxygen uptake during maximal aerobic efforts.

Best L-Citrulline Form for Endurance

Citrulline Malate 2:1 generally works best for endurance because malic acid supports aerobic ATP production. The malate portion improves Krebs cycle efficiency, while L-Citrulline drives vasodilation and ammonia buffering. Together they create a well-rounded endurance support stack for both runners and cyclists.

Timing, Stacking, and Safety for Endurance Athletes

Most athletes get the strongest effect when they take L-Citrulline about 60 minutes before training, which aligns with peak blood levels and nitric oxide production. Endurance athletes often use 6 to 8 grams of Citrulline Malate or 4 to 6 grams of Pure L-Citrulline with 16 to 20 ounces of water on an empty stomach for better absorption. Many stack it with 3 to 5 grams of beta-alanine for muscular endurance and around 50 milligrams of Astragin to support uptake.

L-Citrulline is generally well tolerated, although doses above 10 grams can cause mild digestive discomfort in some athletes. Because it lowers blood pressure through vasodilation, athletes who use antihypertensive medications should speak with a healthcare professional before starting. Bucked Up also offers non-stimulant pre-workouts that include L-Citrulline for athletes who train at night or avoid caffeine.

Consistent daily use usually outperforms single-dose strategies. Researchers recommend body mass-adjusted doses over multiday periods longer than 7 days for full evaluation, which suggests that steady intake builds the strongest endurance gains.

L-Citrulline stands as a well-studied way to support endurance performance for runners and cyclists. Bucked Up formulations provide clinical dosing and absorption support that help athletes get more from each scoop. Bucked Up L-Citrulline Powder (300g) remains a strong choice for athletes who want simple, flexible dosing to chase new personal records.

Frequently Asked Questions

How long does it take for L-Citrulline to work for endurance performance?

L-Citrulline starts working within 60 to 90 minutes, with peak blood levels around 1 to 2 hours after ingestion. For race-day or workout benefits, most athletes take it about 60 minutes before training or competition. The largest endurance gains usually appear with daily use over 7 to 14 days, as nitric oxide production and vascular function adapt. Many athletes notice better pumps and less fatigue in the first week, with peak endurance changes after 2 to 3 weeks of consistent use.

Can L-Citrulline help with altitude training and performance?

L-Citrulline can support altitude training by improving oxygen delivery and use when air oxygen levels drop. Higher nitric oxide production helps offset altitude-related vasoconstriction and keeps blood moving to working muscles. Its role in ammonia detoxification also becomes more valuable when metabolic stress rises at elevation. Endurance athletes training high often pair L-Citrulline with iron and B vitamins to support red blood cell function and oxygen transport.

What is the difference between L-Citrulline timing for runners versus cyclists?

Both runners and cyclists benefit from taking L-Citrulline about 60 minutes before training. Cyclists may feel more benefit during long rides because sustained seated positions can restrict blood flow, which nitric oxide helps counter. Runners who deal with impact-related muscle damage may also add a 3 to 4 gram post-exercise dose to support recovery and reduce soreness. For ultra events longer than 4 hours, athletes in both sports can use extra 2 to 3 gram doses every 2 to 3 hours to help maintain nitric oxide levels.

How does L-Citrulline interact with other common endurance supplements?

L-Citrulline pairs well with many endurance supplements without major conflicts. Beta-alanine supports muscular endurance, while L-Citrulline improves blood flow and oxygen delivery. Caffeine and L-Citrulline also work together, as vasodilation can offset some of caffeine’s vasoconstrictive effects. Creatine and L-Citrulline target different energy systems and can be taken together safely. Athletes should avoid stacking high-dose L-Arginine with L-Citrulline, because this combination can upset digestion and does not improve results, since L-Citrulline already converts to arginine efficiently.

Is L-Citrulline effective for female endurance athletes?

Female endurance athletes gain similar benefits from L-Citrulline as male athletes. Some research suggests women may even see stronger nitric oxide responses because estrogen supports endothelial function. Many female athletes report noticeable reductions in exercise-induced soreness and faster recovery with regular use. Dosing guidelines remain similar for both genders, although smaller athletes under about 120 pounds may do well with 4 to 6 grams of Citrulline Malate. Women can maintain consistent dosing across the menstrual cycle, since hormonal shifts do not significantly change L-Citrulline’s endurance effects.