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HPMC Capsules: What Is the Shell Made Of?
HPMC capsules are shells made from hydroxypropyl methylcellulose, a modified plant fiber, often sold as vegetable capsules. Melonex lists the shell as its first other ingredient. The shell is not part of the 500 mg blend, so it adds no citrulline or arginine. It only holds the powder.
Written by the Melonex numbers deskUpdated · 4 min read
01The shell
What are HPMC capsules made of?
HPMC capsules are made of hydroxypropyl methylcellulose, a cellulose-based material shaped into two halves that lock together around the powder.
Cellulose is plant fiber. HPMC is cellulose that has been modified so it forms a smooth, strong film. That is why the shells get called vegetable capsules.
The Melonex label says it plainly: Hydroxypropyl Methylcellulose (capsule). It is a shell, not an active ingredient.
The shell does not count toward the 500 mg proprietary blend, which covers three amino-acid lines only.
The label names the shell and prints no shell weight, so you will not find one anywhere on the bottle.
02FDA view
Is hydroxypropyl methylcellulose allowed in food?
Yes. A federal food-additive rule says hydroxypropyl methylcellulose may be safely used in food as a film former, thickener, stabilizer and more, under good manufacturing practice (21 CFR 172.874 (HPMC)).
That puts HPMC among materials with a written food rule behind them, which is a lower bar than a test of this exact product.
The rule also requires the material to meet National Formulary specifications. That is a quality standard for the material, not for the Melonex product.
Two limits matter. A food rule does not test a finished supplement, and FDA does not approve supplements before they are sold. The real question for a buyer is what is inside the shell.
The rule covers the material. The 500 mg blend inside has its own limits, shown next.
03Inside it
How much active powder fits in the shell?
The label caps the blend at 500 mg per capsule. By weight order, the citrulline line holds at most 500 mg and the arginine pair at most 333 mg.
Studies of L-citrulline used 3 to 9 g a day (Avicenna J Phytomed 2019, L-citrulline and BP meta-analysis). Studies of L-arginine used 4 to 24 g a day (Am Heart J 2011, L-arginine and BP meta-analysis). A capsule is far below both.
The bars show the ceilings for one and two capsules against those study doses. They are limits, not measured amounts.
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.
No trial tested Melonex. The shell itself carries no citrulline or arginine, so a bigger or smaller shell would not change these ceilings.
04Outside the blend
What else is in the capsule besides the shell?
Two more fillers sit beside the shell: microcrystalline cellulose and magnesium stearate. None is part of the 500 mg blend.
| Ingredient | Likely job | Amount printed |
|---|---|---|
| Hydroxypropyl methylcellulose | Shell | Not printed |
| Microcrystalline cellulose | Bulking filler | Not printed |
| Magnesium stearate | Flow aid | Not printed |
Jobs here are common roles for these materials, not claims from the maker. For the flow aid, see the post on magnesium stearate.
05Your call
Does the shell matter when you pick a supplement?
The shell matters for diet and swallowing, not for what the blend might do. Read it for allergens and sourcing, then move on to the contents.
If a shell or filler could be a problem for you, ask the seller before ordering. Questions go to the order desk at +1 (855) 889-3137.
See the whole panel on the label page and every filler in the other ingredients guide. One bottle holds 60 capsules, enough for 60 days at one a day.
Keep taking prescribed medicine, and tell your doctor about any supplement you add.
Prices listed on the seller's order page; confirm at checkout. The 2-bottle kit costs $158, with $9.99 shipping. Ask your doctor about your medicines first. 60-day money-back guarantee per the seller.
Melonex is not a treatment; it is a dietary supplement. Ask your doctor or pharmacist first if you take blood-pressure medicine, nitrates for chest pain, an erectile-dysfunction drug such as sildenafil or tadalafil, a potassium-sparing diuretic (amiloride, spironolactone, triamterene), a blood thinner, or diabetes medicine, or if you have had a recent heart attack. Arginine and citrulline can add to these. Keep taking prescribed medicine. See side effects and interactions.
06FAQ
Melonex questions people ask
Are HPMC capsules vegan?
HPMC is a plant-based cellulose material, so the shell itself is not animal-derived. The rest of the capsule is separate. Melonex prints no vegan statement and names no source for magnesium stearate, so ask the seller if strict diets matter.
Are HPMC capsules the same as gelatin capsules?
No. Gelatin is made from animal collagen; HPMC is made from modified plant cellulose. Melonex uses the HPMC kind, listed as hydroxypropyl methylcellulose (capsule). The label does not compare the two or claim any benefit for the shell.
Does the HPMC shell count toward the 500 mg?
No. The 500 mg is the proprietary blend of three amino-acid lines. The shell, microcrystalline cellulose and magnesium stearate are listed separately as other ingredients, each with no printed weight.
Can you swallow a Melonex HPMC capsule easily?
The label tells you to take one capsule with an 8 oz. glass of water. It gives no size or dimensions for the capsule, so ask the seller if swallowing is a concern for you.
07Who 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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