Ingredient profile
L-Arginine HCl in Melonex: Third Line, Smallest Ceiling
L-arginine HCl is the third and last line in the Melonex blend, so one capsule holds at most 167 mg of it. HCl is the salt form of the amino acid arginine. Blood-pressure trials of L-arginine used 4-24 g a day, grams not milligrams. No trial has tested Melonex.
Written by the Melonex numbers deskUpdated
01The ingredient
What is L-arginine HCl?
L-arginine HCl is the hydrochloride salt of L-arginine, an amino acid. The HCl part is the salt that keeps the powder stable and easy to blend.
Your body makes arginine and also gets it from meat, dairy, nuts and seeds. A supplement adds more of the same molecule, bound to hydrochloride.
On the Melonex label it sits third in the Proprietary Blend, after L-citrulline DL-malate and L-arginine alpha-ketoglutarate. The blend is 500 mg per capsule. Order on a blend list means weight, from most to least (21 CFR 101.36 (proprietary blends)).
| Name on the label | L-Arginine HCL |
|---|---|
| What it is | L-arginine as the hydrochloride salt |
| Place on the label | 3rd of 3 in the 500 mg proprietary blend |
| Most per capsule | 167 mg (ceiling; real amount not printed) |
| At 2 capsules | at most 333 mg |
| Amount used in research | 4-24 g a day of L-arginine in blood-pressure trials (median 9 g) |
| What research found | About 5 mm Hg systolic drop in 11 small trials at gram doses |
| Main caution | Do not combine with potassium-sparing diuretics; not after a recent heart attack. |
02The number
How many mg of L-arginine HCl are in one Melonex capsule?
At most 167 mg. The label does not print the real amount, but third place caps it at one third of the 500 mg blend.
The math is short. If all three lines weighed the same, each would be about 167 mg. The third line cannot be heavier than that, because the first two must weigh at least as much. It can be lighter.
At the two-capsule label maximum, the ceiling doubles to 333 mg. The two arginine lines together, AKG plus HCl, can weigh at most 333 mg in one capsule and 667 mg in two.
Those are weights of the whole compound, so the amino acid itself is lower still.
L-citrulline DL-malate
≤500 mgplace 1 of 3One capsule's ceiling is 17% of the low end of the studied dose. (Avicenna J Phytomed 2019, L-citrulline and BP meta-analysis)
Both arginine lines together
≤333 mglines 2 and 3 togetherOne capsule's ceiling is 8% of the low end of the studied dose. (Am Heart J 2011, L-arginine and BP meta-analysis)
L-arginine AKG
≤250 mgplace 2 of 3One capsule's ceiling is 8% of the low end of the studied dose. (J Int Soc Sports Nutr 2012, AAKG)
Coral bars: the most one capsule (and the 2-capsule label maximum) can hold, from the label order (21 CFR 101.36 (proprietary blends)). Real amounts are not printed and are likely lower. Teal bars: daily amounts used in studies; the pale extension shows a range. The weights on the label include the malate, alpha-ketoglutarate and HCl parts, so the pure amino acid is less again.
03Research
Does L-arginine affect blood pressure?
In small trials, yes, a little, at gram doses. L-arginine blood pressure results came from 4-24 g a day, many times what a Melonex capsule can hold.
A review pooled 11 randomized trials with 387 people. Oral L-arginine at 4-24 g a day lowered systolic pressure by about 5.4 mm Hg and diastolic by about 2.7 mm Hg versus placebo (Am Heart J 2011, L-arginine and BP meta-analysis). The median dose was 9 g, and most trials ran a few weeks (Drugs.com, L-arginine monograph).
Compare that with the capsule. Both arginine lines together cap at 333 mg, which is about 8% of the 4 g low end. The trials did not use Melonex, and none used this blend.
| Measure | Trials | 1 capsule | 2 capsules |
|---|---|---|---|
| Arginine dose | 4-24 g a day | at most 333 mg | at most 667 mg |
| Systolic change | about -5.4 mm Hg | Not tested | Not tested |
| People studied | 387 | None | None |
Exercise studies of 2-20 g a day found no effect on nitric oxide or blood flow (NIH ODS, Supplements for Exercise). Read the results as small and mixed.
04Side effects
What are the L-arginine side effects?
The common ones are stomach complaints: nausea, belly pain, diarrhea and bloating. Headache, gout flare-ups and low blood pressure are also listed.
Mayo Clinic lists nausea, abdominal pain, diarrhea, bloating, gout, headache, allergy and worse asthma (Mayo Clinic, L-arginine). A national fact sheet says 9-30 g a day most often caused an upset stomach and slightly lower pressure (NIH ODS, Supplements for Exercise). Up to 9 g a day for days or weeks is described as well tolerated; safety past three months is unknown.
Stomach
Nausea, bloating and loose stools lead the list.
Low pressure
Dizziness, fainting or blurry vision can signal pressure below 90/60 (NHLBI, Low blood pressure). Sit down and call your doctor.
Allergy and asthma
Asthma can get worse on arginine.
05Medicines
Which medicines clash with L-arginine?
Blood-pressure drugs, nitrates, erectile-dysfunction drugs, blood thinners, diabetes drugs and potassium-sparing diuretics all call for a conversation first.
Each row below says what the risk is and where it comes from. The label's own caution asks anyone with a known medical condition to see a physician before use.
| If you take | Examples | Why ask first |
|---|---|---|
| Blood-pressure medicines | ACE inhibitors, ARBs, diuretics, calcium channel blockers and others | Arginine and citrulline may add to them; pressure could drop too low (dizzy, faint). (Mayo Clinic, L-arginine) (WebMD, L-citrulline) (NHLBI, Low blood pressure) |
| Nitrates for chest pain | Nitroglycerin, isosorbide | Pressure may drop too low with arginine; citrulline is also flagged. (Mayo Clinic, L-arginine) (Drugs.com, L-arginine monograph) (WebMD, L-citrulline) |
| Erectile-dysfunction drugs (PDE-5) | Sildenafil, tadalafil, vardenafil, avanafil | Pressure may drop too low; these drugs already must not be mixed with nitrates. (Mayo Clinic, L-arginine) (WebMD, L-citrulline) (MedlinePlus, Sildenafil) |
| Potassium-sparing diuretics | Amiloride, spironolactone, triamterene | Mayo Clinic says do not combine with L-arginine: blood potassium can rise. (Mayo Clinic, L-arginine) (NIH ODS, Potassium) |
| Blood thinners and antiplatelets | Anticoagulant and antiplatelet drugs | L-arginine may add to bleeding risk. (Mayo Clinic, L-arginine) |
| Diabetes medicines | Insulin and glucose-lowering drugs | L-arginine might lower blood sugar; doses may need checking. (Mayo Clinic, L-arginine) (Drugs.com, L-arginine monograph) |
| After a recent heart attack | Any plan to add arginine | One trial stopped early: 6 deaths on 9 g a day of arginine, none on placebo. (ACC, VINTAGE MI trial summary) |
Never stop or change a prescribed drug because you added a supplement.
06Potassium
Why does the HCl part matter for potassium?
Arginine can raise blood potassium in some people, and the risk is higher with kidney or liver disease or with certain drugs.
Drugs.com reports high potassium in people with liver or kidney impairment taking arginine (Drugs.com, L-arginine monograph). Mayo Clinic says not to combine arginine with the potassium-sparing diuretics amiloride, spironolactone and triamterene (Mayo Clinic, L-arginine).
People on ACE inhibitors or with kidney disease are told to ask before using potassium products (NIH ODS, Potassium).
- Kidney or liver disease: ask a clinician first
- Potassium-sparing diuretic: do not combine without advice
- ACE inhibitor: ask before adding potassium sources
07Heart attack
Is L-arginine safe after a heart attack?
No recommendation exists for it. Mayo Clinic says arginine is not recommended after a recent heart attack, and one trial stopped early.
In the VINTAGE MI trial, 153 people took 9 g of arginine a day or placebo after a first heart attack. Six died on arginine and none on placebo (ACC, VINTAGE MI trial summary). The trial stopped early.
That dose is about 54 times this line's 167 mg ceiling. The full story is on arginine after a heart attack.
See also arginine vs citrulline and the price.
08FAQ
L-arginine HCl questions
How much L-arginine HCl is in Melonex?
At most 167 mg per capsule, and the real amount is not printed. The blend is 500 mg and lists the HCl line third, so it cannot outweigh the first two. At two capsules the ceiling is 333 mg.
Is L-arginine HCl the same as L-arginine?
Nearly. It is arginine bound to hydrochloride, a salt, so 167 mg of the compound holds less than 167 mg of pure arginine.
Can L-arginine HCl cause low blood pressure?
It can in some people, especially with blood-pressure drugs. Mayo Clinic warns pressure may drop too low (Mayo Clinic, L-arginine). Below 90/60 or with dizziness, sit down and call your doctor (NHLBI, Low blood pressure).
Does L-arginine HCl affect potassium?
It might in people with kidney or liver problems or on potassium-sparing diuretics (Mayo Clinic, L-arginine) (Drugs.com, L-arginine monograph). Ask a pharmacist before using it if either applies to you.
What dose of L-arginine did blood pressure studies use?
Between 4 and 24 g a day, with a median near 9 g, across 11 trials and 387 people (Am Heart J 2011, L-arginine and BP meta-analysis) (Drugs.com, L-arginine monograph). One Melonex capsule holds at most 333 mg from both arginine lines.
Can I take L-arginine HCl while pregnant or nursing?
Only under a health care provider. Data on pregnancy and nursing are minimal (Drugs.com, L-arginine monograph), and the Melonex label asks pregnant or nursing mothers to consult a physician first.
09Who wrote this
Written and reviewed by
Pages built from the label, the seller's materials and linked NIH, FDA, CDC, AHA, FTC and peer-reviewed sources.
Last updated . Read how we write and how we check reviews. This website is run by Melonexheart, which describes itself as a U.S. authorized Melonex merchant. It is not the manufacturer or the label's distributor, and we cannot independently verify the 'authorized' status. We are paid when you buy through our order links.
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