Home Ingredients PepForm® Citrulline Peptides (L-Citrulline — Glanbia Nutritionals)
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PepForm® Citrulline Peptides (L-Citrulline — Glanbia Nutritionals)

Evidence Level
Limited
2 Clinical Trials
3 Documented Benefits
2/5 Evidence Score

PepForm® Citrulline Peptides bind free L-citrulline to whey-derived peptides for clean solubility and taste. L-citrulline is an efficient nitric-oxide booster: the body converts it to arginine and then to nitric oxide, and it tends to raise blood arginine more effectively than arginine taken directly. Citrulline in general is one of the more heavily studied 'pump' and blood-flow ingredients, examined for exercise performance and blood pressure, though the results are mixed: pooled analyses show a small benefit for high-intensity strength work and a modest blood pressure drop, but no benefit for endurance or aerobic performance and no overall effect on body composition. Honest framing: a search of the published medical literature turns up no study of PepForm itself, so everything on this page is borrowed from free L-citrulline, citrulline malate or watermelon rather than measured on this branded peptide-bound form, and PepForm's specific absorption and solubility figures are manufacturer data that no independent trial has checked.

Studied Dose 6-8 g citrulline malate taken 40-60 minutes before exercise is the dose used in most strength-training trials. Note that L-citrulline and citrulline malate are not interchangeable at the same number: 8 g of citrulline malate supplies roughly 4.5 to 6 g of actual citrulline depending on the ratio used, and trials of pure L-citrulline generally used 2.4-6 g/day, so 6-8 g is a citrulline malate figure rather than an L-citrulline one. No dose has been established for the PepForm peptide-bound form specifically.
Active Compound L-Citrulline bound to whey-derived peptides (PepForm® peptide carrier technology) for improved solubility and flavor. Glanbia also markets the peptide binding as improving absorption, but no published human study has compared the absorption of PepForm citrulline against ordinary L-citrulline, so treat the absorption claim as unverified manufacturer marketing.

Benefits

Nitric oxide, pump, and blood flow

Citrulline raises blood arginine and markers of nitric oxide more efficiently than arginine itself, because oral arginine is largely broken down in the gut before it reaches the bloodstream. This has been measured directly in healthy volunteers. Note the honest limit: raising the arginine and nitric oxide markers is not the same as producing a visible or measurable 'pump', and in the controlled dosing study that measured it, flow-mediated dilation of the artery did not actually improve over baseline.

Supported by Trial 1, Trial 2

Exercise performance and recovery

Meta-analyses of generic citrulline find a small benefit for high-intensity strength and power work, roughly three extra repetitions before failure across a session, and a reduction in perceived exertion and in muscle soreness at 24 hours. The benefit is genuinely small and the picture is uneven: soreness at 48 and 72 hours, blood lactate, endurance time to exhaustion and aerobic performance were all unchanged, and a separate pooled analysis of 21 trials found no overall effect on fat-free mass, fat mass or body weight. None of these trials used PepForm.

Supported by Trial 1, Trial 2

Blood pressure support

Pooled trial data in middle-aged and older adults show a modest average drop of about 4 mmHg systolic and 2.5 mmHg diastolic. Two honest caveats: the pooled trials mixed L-citrulline supplements with plain watermelon intake, and the largest effect came from the subgroup that took citrulline together with L-arginine rather than citrulline on its own. This is a general citrulline finding, not a PepForm finding, and it is not a treatment for high blood pressure.

Supported by Trial 2

Mechanism of action

1

Citrulline-to-arginine-to-nitric-oxide pathway

Citrulline bypasses the gut and liver breakdown that limits oral arginine, recycling efficiently into arginine and then nitric oxide. The step from higher nitric oxide markers to actually wider blood vessels is less well demonstrated: in the controlled dosing study that measured it, urinary nitric oxide metabolites rose but flow-mediated dilation did not improve.

2

Peptide-bound delivery

Whey-peptide binding is described by the manufacturer as giving a soluble, palatable form well suited to pre-workout drinks and powders. Solubility and taste are formulation properties, not health mechanisms, and no published study has tested whether binding citrulline to whey peptides changes how much citrulline reaches the blood or what it does once there.

Clinical trials

1
Citrulline and Body Composition Review (null result)

Systematic review and dose-response meta-analysis of 21 randomized controlled trials (Nutrients, 2025). Generic citrulline or watermelon, not PepForm.

Participants pooled from 21 randomized controlled trials

The headline result was null: across 21 randomized trials, citrulline supplementation had no overall effect on body mass index, body weight, fat mass, waist circumference, body fat percentage or fat-free mass. Exploratory subgroup analyses hinted at less fat mass in participants over 40 and at doses above 6 g/day, and at more fat-free mass in trials lasting 3 to 8 weeks, but the authors themselves called these findings exploratory and asked for better-controlled trials. This review measured body composition only, not exercise performance, and it did not test PepForm.

2
Citrulline and Blood Pressure Review

Systematic review and meta-analysis of 15 randomized controlled trials, 415 participants (Clinical Nutrition ESPEN, 2025). Generic L-citrulline and watermelon, not PepForm.

Adults

Across 15 randomized trials and 415 participants, L-citrulline supplementation or watermelon intake lowered systolic blood pressure by about 4 mmHg and diastolic by about 2.5 mmHg. The subgroup that combined L-citrulline with L-arginine did substantially better, about 10 mmHg systolic, which means the headline figure is not attributable to citrulline alone in every trial. The pooled sample is small, the population was middle-aged and older adults, and PepForm was not used.

Side effects and drug interactions

Common Potential side effects

Generally well tolerated, but not free of gut effects: in the trial that popularized the 8 g citrulline malate dose, about 15 percent of participants reported stomach discomfort.
Can mildly lower blood pressure.
Contains whey-derived peptides; avoid with milk allergy.
No serious safety signals have been reported at typical doses, though most trials were short and none tested the PepForm peptide-bound form.

Important Drug interactions

Antihypertensives and nitrates: additive blood-pressure lowering — caution.
PDE5 inhibitors: additive vasodilation.
No other well-documented interactions, though formal drug interaction studies of citrulline are scarce and none exist for the PepForm form.

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Frequently asked questions about PepForm® Citrulline Peptides (L-Citrulline — Glanbia Nutritionals)

Why is PepForm Citrulline popular in pre-workouts?

Citrulline is an efficient nitric-oxide booster for blood flow and the muscle pump, and the PepForm peptide-bound form is sold on the basis that it dissolves cleanly without the grit or bitterness of plain citrulline, which suits ready-to-drink and powder formats. Those are taste and mixing properties claimed by the manufacturer, not health benefits, and no published study has compared PepForm with plain citrulline on either taste or results.

Citrulline vs arginine for nitric oxide?

Citrulline usually wins. Taken orally it raises blood arginine and nitric oxide more reliably than arginine itself, because arginine is largely broken down before it reaches the bloodstream.

What is PepForm Citrulline Peptides?

PepForm® Citrulline Peptides bind free L-citrulline to whey-derived peptides for clean solubility and taste. L-citrulline is an efficient nitric-oxide booster: the body converts it to arginine and then to nitric oxide, and it tends to raise blood arginine more effectively than arginine taken directly.

What is PepForm Citrulline Peptides used for?

PepForm Citrulline Peptides is researched primarily for Athletic Performance, Cardiovascular, and Muscle & Recovery. Citrulline raises blood arginine and markers of nitric oxide more efficiently than arginine itself, because oral arginine is largely broken down in the gut before it reaches the bloodstream.

What is the recommended dosage of PepForm Citrulline Peptides?

The clinically studied dose is 6-8 g citrulline malate taken 40-60 minutes before exercise is the dose used in most strength-training trials. Note that L-citrulline and citrulline malate are not interchangeable at the same number: 8 g of citrulline malate supplies roughly 4. Always follow the product label and check with a healthcare provider for personal advice.

Is PepForm Citrulline Peptides safe, and does it have side effects?

For most healthy adults, PepForm Citrulline Peptides is well tolerated at studied doses. Reported effects can include: Generally well tolerated, but not free of gut effects: in the trial that popularized the 8 g citrulline malate dose, about 15 percent of participants reported stomach discomfort. Can mildly lower blood pressure. It may also interact with some medications. PepForm Citrulline Peptides is not right for everyone, so check with a healthcare provider first if you are pregnant or breastfeeding, have a medical condition, or take prescription medication.

Does PepForm Citrulline Peptides interact with any medications?

Possible interactions include: Antihypertensives and nitrates: additive blood-pressure lowering — caution. PDE5 inhibitors: additive vasodilation. If you take prescription medication, check with a pharmacist or doctor before using it.

How strong is the scientific evidence for PepForm Citrulline Peptides?

NutraSmarts rates the evidence for PepForm Citrulline Peptides as Limited (2 out of 5). It is backed by 2 clinical trials and 9 cited references summarized on this page. A higher rating reflects more, larger, and better-designed human studies.

References(9 citations)

Evidence ratings on NutraSmarts are based on the totality of human clinical research, with emphasis on randomized controlled trials, meta-analyses, and systematic reviews. The references below directly support claims made throughout this page.

  1. Ashtary-Larky D, Mohammadi S, Mousavi SAH, Hajizadeh L, Candow DG, Forbes SC, et al. Effects of Citrulline or Watermelon Supplementation on Body Composition: A Systematic Review and Dose-Response Meta-Analysis. Nutrients. 2025;17(19). doi: 10.3390/nu17193126.PubMedUsed to support: Pooled analysis of 21 randomized trials of citrulline or watermelon supplementation found no overall effect on body weight, body mass index, fat mass, body fat percentage, waist circumference or fat-free mass; only exploratory subgroups hinted at benefit. Limitations: this is generic citrulline and watermelon, not the PepForm peptide-bound form, and the review measured body composition rather than exercise performance.
  2. Luo P, Chen J, Liu K, Zhang J Does l-citrulline supplementation and watermelon intake reduce blood pressure in middle-aged and older adults? A systematic review and meta-analysis of randomized controlled trials. Clinical Nutrition ESPEN. 2025;69:653-664. doi: 10.1016/j.clnesp.2025.07.1130.PubMedUsed to support: Pooled analysis of 15 randomized trials in 415 middle-aged and older adults found systolic blood pressure about 4 mmHg lower and diastolic about 2.5 mmHg lower with L-citrulline supplementation or watermelon intake. Limitations: the trials mixed supplements with whole watermelon, the largest reduction came from a subgroup that combined citrulline with L-arginine so the effect is not citrulline alone, the total sample is small, and no trial used the PepForm branded form.
  3. Trexler ET, Persky AM, Ryan ED, et al. Acute Effects of Citrulline Supplementation on High-Intensity Strength and Power Performance: A Systematic Review and Meta-Analysis. Sports Med. 2019;49(5):707-718..PubMedUsed to support: Meta-analysis of 12 studies and 198 participants found citrulline supplementation improved high-intensity strength and power outcomes compared with placebo, but the pooled effect was small: a standardized mean difference of 0.20, with a confidence interval of 0.01 to 0.39 that only just clears no effect at all. Trials had to use at least 3 g taken at least 30 minutes before testing. Limitation: every trial used generic L-citrulline or citrulline malate, not the PepForm peptide-bound form.
  4. Vårvik FT, Bjørnsen T, Gonzalez AM Acute Effect of Citrulline Malate on Repetition Performance During Strength Training: A Systematic Review and Meta-Analysis. Int J Sport Nutr Exerc Metab. 2021;31(4):350-358..PubMedUsed to support: Meta-analysis of 8 randomized trials in 137 participants found that 6-8 g of citrulline malate taken 40-60 minutes before lifting added about 3 repetitions to failure, a 6.4 percent increase, with a small effect size of 0.196. The lower-body subgroup only reached a trend (p = 0.051) and the upper-body subgroup was not significant (p = 0.131). This is where the 6-8 g dose figure comes from, and it refers to citrulline malate rather than pure L-citrulline. Limitation: PepForm itself was not tested.
  5. Rhim HC, Kim SJ, Park J, et al. Effect of citrulline on post-exercise rating of perceived exertion, muscle soreness, and blood lactate levels: A systematic review and meta-analysis. J Sport Health Sci. 2020;9(6):553-561..PubMedUsed to support: Meta-analysis of 13 trials in 206 participants found that citrulline reduced rating of perceived exertion and reduced muscle soreness measured 24 hours after exercise. Soreness at 48 and 72 hours and blood lactate were not significantly reduced. Limitations: small acute trials of generic citrulline and citrulline malate, not the PepForm peptide-bound form.
  6. Viribay A, Fernández-Landa J, Castañeda-Babarro A, et al. Effects of Citrulline Supplementation on Different Aerobic Exercise Performance Outcomes: A Systematic Review and Meta-Analysis. Nutrients. 2022;14(17)..PubMedUsed to support: Meta-analysis of 10 placebo-controlled trials found citrulline supplementation produced no significant benefit for aerobic performance, rating of perceived exertion, oxygen uptake kinetics or blood lactate. Aerobic and endurance work is where citrulline consistently fails to show an effect, in contrast to short high-intensity efforts. Limitation: generic citrulline, not the PepForm branded form.
  7. Harnden CS, Agu J, Gascoyne T Effects of citrulline on endurance performance in young healthy adults: a systematic review and meta-analysis. J Int Soc Sports Nutr. 2023;20(1):2209056..PubMedUsed to support: Meta-analysis of 9 randomized trials in 158 recreationally active young adults found no significant effect of acute citrulline supplementation on endurance time to exhaustion or time to completion. Endurance athletes should not expect a benefit. Limitations: the evidence base is small, and the trials used generic citrulline rather than the PepForm peptide-bound form.
  8. Schwedhelm E, Maas R, Freese R, et al. Pharmacokinetic and pharmacodynamic properties of oral L-citrulline and L-arginine: impact on nitric oxide metabolism. Br J Clin Pharmacol. 2008;65(1):51-9..PubMedUsed to support: Randomized placebo-controlled crossover study in 20 healthy volunteers taking oral L-citrulline or L-arginine for one week: citrulline raised plasma arginine dose-dependently and more effectively than arginine itself, and 3 g twice daily increased urinary nitrate and cyclic GMP. Importantly, no treatment improved flow-mediated dilation of the artery over baseline, so this backs the citrulline-to-arginine conversion described in the mechanisms section but not a demonstrated vessel-widening benefit. Limitation: free L-citrulline, not the PepForm form.
  9. Pérez-Guisado J, Jakeman PM Citrulline malate enhances athletic anaerobic performance and relieves muscle soreness. J Strength Cond Res. 2010;24(5):1215-22..PubMedUsed to support: Randomized double-blind crossover trial in 41 men: a single 8 g dose of citrulline malate increased bench press repetitions to fatigue and reduced muscle soreness at 24 and 48 hours, but about 15 percent of participants reported stomach discomfort, which is why the safety section notes citrulline is not entirely free of gut effects. Limitations: a single small trial reporting a much larger performance effect than the later pooled analyses found, using citrulline malate rather than the PepForm peptide-bound form.