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Citrulline vs Arginine for Nitric Oxide: How They Differ and Why BloodPril Lists Both
L-arginine is the amino acid your body uses to make nitric oxide. L-citrulline is a step earlier: the body turns it into arginine. Some products pair them to feed the same pathway two ways. BloodPril lists citrulline malate plus two arginine salts in one 500 mg blend, and nobody has measured its effect on nitric oxide.
Written by the BloodPril editorial teamUpdated · 8 min read
Short answer
L-arginine vs L-citrulline: what is the difference?
Arginine is the direct raw material for nitric oxide. Citrulline is a raw material for arginine. One feeds the pathway at the end, the other one step before.
Both are amino acids your body makes and also gets from food. Neither is a drug. In supplements, both are sold under the same promise of better blood flow, which is why people compare them.
The two are linked in a loop. Your body turns citrulline into arginine. When cells then use arginine to make nitric oxide, citrulline is left over, ready to be recycled.
The pathway
How does the body turn citrulline into arginine?
Citrulline travels in the blood to the kidneys, which convert most of it into arginine. That arginine joins the body's general supply.
Citrulline arrives
From food, from your own metabolism, or from a supplement.
The kidneys convert it
Citrulline becomes arginine and enters the bloodstream.
Cells use arginine
The lining of blood vessels uses arginine to make nitric oxide.
Vessels relax
Nitric oxide signals the vessel wall to relax. Citrulline is left over and can be recycled.
So citrulline does not make nitric oxide by itself. It works, if at all, by adding to the arginine pool. Our how BloodPril works page draws the same pathway step by step.
The big question
Which one actually raises nitric oxide?
Both are nitric oxide precursors, but no one has measured nitric oxide in people taking BloodPril. Any claim that the capsule "boosts" it by a set amount has no data behind it.
For arginine, the best-known blood pressure evidence is a 2011 meta-analysis of 11 small trials at 4 to 24 grams a day, which found a small average drop versus placebo (Dong et al., Am Heart J 2011). Our walk-through of that research explains the numbers.
For citrulline, research on blood pressure exists, but it is small. We could not open and check a citrulline study page ourselves, so we give no citrulline doses or effect sizes here.
Citrulline figures circulate widely online, often without a source you can open. We only print a number when we have read where it came from.
On the label
How do the three forms on the BloodPril label compare?
BloodPril's label names three ingredient forms in one 500 mg blend. Two are forms of the same amino acid, arginine, each bound to a different partner.
Label order matters. Blend ingredients appear in order of weight, heaviest first (FDA, Labeling guide). So L-citrulline DL-malate is the largest single part, though its exact amount is not printed.
| Label name | Amino acid delivered | Partner molecule | Amount per capsule | Usually sold for |
|---|---|---|---|---|
| L-Citrulline dl-Malate | Citrulline (becomes arginine) | Malic acid | Not published | Blood flow and sports "pump" products |
| L-Arginine (Alpha-Ketoglutarate dihydrate) | Arginine | Alpha-ketoglutarate | Not published | Gym "nitric oxide booster" products |
| L-Arginine HCL | Arginine | Hydrochloride | Not published | General arginine supplements |
- 1L-citrullineL-Citrulline dl-Malate · Not disclosed (part of the 500 mg blend)
- 2Arginine AKGL-Arginine (Alpha-Ketoglutarate dihydrate) · Not disclosed (part of the 500 mg blend)
- 3L-arginine HClL-Arginine HCL · Not disclosed (part of the 500 mg blend)
Listed in label order, from most to least by weight, inside one 500 mg proprietary blend per capsule.
Formulas
Why is citrulline often paired with arginine?
Pairing them feeds the same arginine supply from two directions: directly, and through conversion. That is the logic. Whether a combination does more than either alone has not been tested in BloodPril.
Arginine, straight in
Arginine is the direct building block. It is also the form with the most blood pressure research, all at gram doses.
Citrulline, converted
The kidneys turn citrulline into arginine, so it adds to the same supply a step later.
The combination
No published trial of this three-form blend exists that we could find. The pairing is a design idea, not a measured result.
You will often read that citrulline "survives digestion better" than arginine. That is a common supplement-industry argument. We have not verified it against a source we could open, so we report it as a claim, not a fact.
Two arginines
Does arginine AKG differ from arginine HCl?
Both deliver L-arginine. The difference is the partner it is bound to: alpha-ketoglutarate in AAKG, hydrochloride in arginine HCl.
AAKG is sold mainly to gym users as a "nitric oxide booster". Arginine HCl is a common, simple salt of the amino acid. We found no blood pressure figures for AAKG itself, so the arginine research and cautions apply to both (Mayo Clinic, L-arginine) (Dong et al., Am Heart J 2011).
- Some of each salt's weight belongs to its partner molecule.
- The label gives no split between the two arginine forms.
- More detail sits on the arginine AKG page.
Category
Do nitric oxide supplements help blood pressure?
The evidence is thin and dose-bound. Arginine showed a small average effect at 4 grams a day or more (Dong et al., Am Heart J 2011). Exercise studies at 2 to 20 grams found little effect on performance (ODS, Exercise supplements).
BloodPril's whole blend is 500 mg per capsule, and 1,000 mg at the two-capsule maximum. That is a quarter of the lowest arginine trial dose, before splitting it three ways.
Because citrulline becomes arginine, the same warnings apply. With blood pressure drugs, nitrates or sildenafil, pressure can drop too low, and arginine is not advised after a recent heart attack (Mayo Clinic, L-arginine). Ask your doctor first, and keep taking your prescribed medicine.
Sources
Where do these facts come from?
The pathway itself is standard biochemistry. Doses, effects and cautions come from the sources below.
- Effect of oral L-arginine supplementation on blood pressure: a meta-analysis of randomized, double-blind, placebo-controlled trials. Dong JY, Qin LQ, Zhang Z, et al. American Heart Journal 162(6):959-965, 2011.11 trials, 387 people, 4 to 24 g of L-arginine a day: systolic down 5.39 mm Hg and diastolic down 2.66 mm Hg versus placebo.
- L-arginine. Mayo Clinic, 2026.Not advised after a recent heart attack. With nitrates or sildenafil blood pressure can drop too low; adds to blood pressure drugs.
- Dietary Supplements for Exercise and Athletic Performance: Fact Sheet for Health Professionals. NIH Office of Dietary Supplements, 2026.Arginine studies used 2-20 g a day with little effect on performance.
- Dietary Supplement Labeling Guide: Chapter IV. Nutrition Labeling. U.S. Food and Drug Administration, 2005.A proprietary blend shows only its total weight and lists ingredients from most to least by weight.
FAQ
Citrulline vs arginine: common questions
L-arginine vs L-citrulline: which one actually raises nitric oxide?
Both feed nitric oxide production, because citrulline is converted into arginine. Which raises it more in a given product is not known without measurement, and no one has measured nitric oxide in people taking BloodPril. Treat any fixed boost figure on a sales page with caution.
Is citrulline malate the same as L-citrulline?
Citrulline malate is L-citrulline bound to malic acid, a fruit acid. Part of its weight is the malate partner, so a gram of citrulline malate holds less than a gram of citrulline. BloodPril lists L-citrulline DL-malate without a separate amount.
How much citrulline is in BloodPril?
The label does not say. Citrulline malate is listed first in the 500 mg blend, so it is the largest single ingredient by weight. That means at least a third of the blend, about 167 mg per capsule, but the exact figure is not printed.
Why does BloodPril have two kinds of arginine?
The label lists arginine bound to alpha-ketoglutarate and arginine bound to hydrochloride. Each one supplies arginine. The brand does not explain the choice, and no amount is given for either, so the label cannot tell you how much arginine you get.
Can I take citrulline with blood pressure medicine?
Ask your doctor first. Citrulline becomes arginine, and arginine can add to blood pressure drugs. With nitrates or sildenafil, pressure can drop too low. Never stop or change a dose on your own.
Is citrulline better than arginine for blood pressure?
That has not been settled by evidence we could verify. Arginine has a pooled meta-analysis at gram doses showing a small effect. Citrulline research on blood pressure exists but is small, and we do not quote figures we could not check.
Who wrote this
Written and reviewed by
Plain-language pages built from the label, the sales page and linked public health sources.
Last updated . Read our editorial standards and how we check reviews. This website is run by a U.S. shop that sells BloodPril, not by the manufacturer. We earn money when you buy through our order links.
Keep reading
More about BloodPril
L-citrulline
What citrulline DL-malate is, how it becomes arginine, and why its cautions match arginine's.
Read moreArginine AKG
What the AKG partner is, why AAKG is sold to gym users, and why the arginine evidence stays the same.
Read moreHow it works
Arginine, citrulline and nitric oxide explained simply, plus the gap between the BloodPril dose and the research.
Read moreBloodPril U.S. shop
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