U.S. stocking partner for VapoCept30 capsules · 30 days665.5 mg declared, 7 names60-day window from purchase
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Salt weight and base weight

This is the most useful thing on this website, because it applies to every amino acid product on every shelf, and almost nobody checks it.

Revised By VapoCept Editorial DeskReviewed by Dr. Mary Cunningham, neuropsychologistReading time 9 min

Quick answer

When a label says “L-Arginine AKG 2:1, 200 mg”, the 200 mg is the weight of the salt. Only 70.5% of that is arginine, so the entry delivers 140.9 mg.

Across this whole label, 600 mg of declared amino acid entries deliver 536 mg of actual amino acid. The missing 64 mg is acid.

Two different numbers

The distinction

Amino acids are often sold as salts rather than as free bases, because salts are more stable, easier to handle, and sometimes better absorbed. That is ordinary chemistry and there is nothing wrong with it.

What matters to a buyer is which weight the label is reporting. “500 mg of L-arginine HCl” and “500 mg of L-arginine” are different products, and the first contains less arginine than the second. US labelling does not require the base weight to be disclosed separately, so most labels report the salt and say nothing.

How to spot it in two seconds

Look for anything after the amino acid name: HCl, hydrochloride, AKG, alpha-ketoglutarate, malate, citrate, aspartate, a ratio like 2:1. Every one of those means the declared weight includes something that is not the amino acid. A bare name — “L-Arginine”, “Beta-Alanine” — usually means the free form, where declared weight and substance weight are the same thing.

On this label, four of the five amino acid entries carry a modifier and one does not. That is a well-designed panel to learn on.

How the fraction is derived

The arithmetic

The fraction of a salt that is the amino acid is a ratio of molecular weights, and it is fixed by chemistry rather than by the manufacturer. For a salt of one amino acid molecule and one acid molecule, the fraction is the amino acid's molecular weight divided by the sum of both.

The molecular weights used on this site, every one from the NIST Chemistry WebBook.
CompoundFormulaMolecular weight
L-arginineC6H14N4O2174.2010 g/mol
alpha-ketoglutaric acidC5H6O5146.0981 g/mol
L-citrullineC6H13N3O3175.1857 g/mol
hydrogen chlorideClH36.461 g/mol
malic acidC4H6O5134.0874 g/mol
beta-alanineC3H7NO289.0932 g/mol

Scroll this table sideways →

Nothing on this page needs any figure that is not in that table. Anyone can reproduce every number below with a calculator.

The 2:1 is a molar ratio, and that is verifiable

It would be easy to assume “2:1” means something vague. It does not. PubChem's entry for L-arginine alpha-ketoglutarate 2:1, CID 76045315, carries the molecular formula C17H34N8O9 — which is exactly two molecules of C6H14N4O2 plus one of C5H6O5. Two arginines, one alpha-ketoglutarate. A separate PubChem entry, CID 3083894, covers the 1:1 salt, which is a different substance.

The four conversions

Worked, one entry at a time

L-Arginine AKG 2:1, declared 200 mg

Two arginine molecules weigh 2 × 174.2010 = 348.402. Add one alpha-ketoglutarate at 146.0981 and the salt weighs 494.500. Arginine is therefore 348.402 ÷ 494.500 = 70.46% of it.

200 mg × 0.7046 = 140.9 mg of arginine. The remaining 59.1 mg is alpha-ketoglutaric acid.

L-Citrulline HCl, declared 100 mg

Citrulline at 175.1857 plus hydrogen chloride at 36.461 gives 211.647. Citrulline is 175.1857 ÷ 211.647 = 82.77%.

100 mg × 0.8277 = 82.8 mg of citrulline.

L-Citrulline Malate, declared 100 mg, ratio not stated

This is the one the label leaves open. At the nominal 2:1, two citrullines weigh 350.371, plus malic acid at 134.0874 gives 484.459, so citrulline is 72.32% — 72.3 mg.

At 1:1 the same 100 mg delivers 56.6 mg. At the 1.6:1 that published analysis found to be typical of commercial material, 67.6 mg. At the 1.1:1 found at the low end, 59.0 mg. The label does not say which, so the honest answer is a range of 56.6 to 72.3 mg, and this site uses the top of it throughout.

L-Arginine base and Beta-Alanine

Neither carries a modifier, so the declared weight is the substance. 200 mg of arginine and 40 mg of beta-alanine, straight through.

Every amino acid entry, converted.
EntryDeclaredFractionSubstance delivered
L-Arginine, base200 mg100%200.0 mg
L-Arginine AKG 2:1200 mg70.5%140.9 mg
L-Citrulline HCl100 mg82.8%82.8 mg
L-Citrulline Malate, at 2:1100 mg72.3%72.3 mg
Beta-Alanine40 mg100%40.0 mg
Total640 mg—536.0 mg

Scroll this table sideways →

Proportion

What this does and does not prove

It is worth being careful about how much weight to put on this page.

The salt arithmetic costs this label about 104 mg across its amino acid entries — roughly 16% of what the declared weights suggest. That is a real difference and it is not the difference that decides anything here. Even if every gram declared were pure amino acid, arginine would still need nine capsules and beta-alanine would still need sixty.

So the salt question is not the argument against this product. It is a skill worth having, it applies to every amino acid label you will ever read, and on a product where the doses were otherwise adequate it could be the whole story. Here it is a footnote to a larger number.

Where it would matter most

Compare two arginine products at $30 each, one declaring 1,000 mg of L-arginine HCl and one declaring 1,000 mg of free-base L-arginine. The hydrochloride is about 82.7% arginine, so the first gives you 827 mg and the second 1,000 mg. That is a 21% price difference hiding in a footnote neither label prints.

Not necessarily a trick

Why labels do it this way

It would be easy to read salt declarations as deliberate inflation. Sometimes they are. Often they are not, and the honest reasons are worth knowing.

  1. It is what the manufacturer bought. The raw material is purchased, weighed and blended as a salt, so the salt weight is the number that exists in the batch record.
  2. Salts are more stable. Free-base amino acids can be hygroscopic or unstable; a hydrochloride is usually easier to handle and store.
  3. Some salts absorb differently. That is the formulator's argument for citrulline malate over plain citrulline, and it is not an unreasonable one.
  4. The counter-ion sometimes does something. Malate enters the citric acid cycle; alpha-ketoglutarate has its own literature. Whether either matters at these amounts is a separate question.
  5. Nothing requires disclosure. A label reporting salt weight is a compliant label, which means there is no pressure on anyone to do the arithmetic for you.

The best labels state both: “L-Arginine HCl 1,000 mg (providing 827 mg L-arginine)”. They exist, they are a minority, and they are identifiable at a glance. A label that does that is telling you something about how it thinks about its buyer.

Four steps

The habit to take away

  1. Read past the amino acid name to whatever follows it.
  2. If there is a salt or a ratio, the declared weight is not the substance weight.
  3. Look up the two molecular weights. NIST's Chemistry WebBook is free and authoritative and takes about thirty seconds.
  4. Divide, multiply, and compare that number against the research rather than the one on the front of the tub.

Four steps, about two minutes, and it works on every pre-workout, every amino blend and every nitric oxide product on the shelf. It is the most portable thing on this website and it does not require trusting us about anything.

The arithmetic it feeds →The longer guides →The shorter version →

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Sources

References

Every source below was opened and read during this build. Nothing here cites a study we did not read, and no identifier on this site was written from memory. Where a claim could not be verified, the page says so instead of using it.

  1. U.S. Government Publishing Office21 CFR 101.93 — Certain types of statements for dietary supplements — eCFR.gov · source
  2. U.S. Food and Drug AdministrationSmall Entity Compliance Guide on Structure/Function Claims — FDA.gov · source
  3. U.S. Food and Drug Administration — 2000Regulations on Statements Made for Dietary Supplements Concerning the Effect of the Product on the Structure or Function of the Body, final rule — 65 Federal Register 1000 · 65 FR 1000 · source
  4. U.S. Food and Drug AdministrationGuidance for Industry: Substantiation for Dietary Supplement Claims Made Under Section 403(r)(6) — FDA.gov · source
  5. U.S. Food and Drug AdministrationQuestions and Answers on Dietary Supplements — FDA.gov · source
  6. U.S. Federal Trade Commission — 2022Health Products Compliance Guidance — FTC.gov · source
  7. National Institute on AgingCognitive Health and Older Adults — NIA.NIH.gov · source
  8. National Center for Complementary and Integrative HealthDietary Supplements and Cognitive Function, Dementia, and Alzheimer’s Disease: What the Science Says — NCCIH.NIH.gov · source
  9. U.S. Food and Drug AdministrationDaily Value on the Nutrition and Supplement Facts Labels — FDA.gov · source
  10. NIH Office of Dietary SupplementsNiacin — Health Professional Fact Sheet — ods.od.nih.gov · source
  11. NIH Office of Dietary SupplementsCalcium — Health Professional Fact Sheet — ods.od.nih.gov · source
  12. Böger — 2007The Pharmacodynamics of L-Arginine — The Journal of Nutrition · DOI 10.1093/jn/137.6.1650S · source
  13. Shiraseb, Asbaghi, Bagheri, Wong, Figueroa, Mirzaei — 2022Effect of L-Arginine Supplementation on Blood Pressure in Adults: a systematic review and dose–response meta-analysis — Advances in Nutrition · DOI 10.1093/advances/nmab155 · PMID 34891179 · source
  14. Mone, Pansini, Jankauskas et al. — 2022L-Arginine Enhances the Effects of Cardiac Rehabilitation on Physical Performance: new insights for managing cardiovascular patients during the COVID-19 pandemic — Frontiers in Cardiovascular Medicine · DOI 10.3389/fcvm.2022.868521 · source
  15. Schwedhelm, Maas, Freese et al. — 2008Pharmacokinetic and pharmacodynamic properties of oral L-citrulline and L-arginine: impact on nitric oxide metabolism — British Journal of Clinical Pharmacology · DOI 10.1111/j.1365-2125.2007.02990.x · PMID 17662090 · source
  16. Campbell, Roberts, Kerksick et al. — 2006Pharmacokinetics, safety, and effects on exercise performance of L-arginine α-ketoglutarate in trained adult men — Nutrition, volume 22 · source
  17. National Library of MedicineL-Arginine alpha-ketoglutarate 2:1 — PubChem CID 76045315, formula C17H34N8O9 — PubChem · CID 76045315 · source
  18. Suzuki, Morita, Kamimura, Miyazawa — 2016Oral L-citrulline supplementation enhances cycling time trial performance in trained male cyclists — Journal of the International Society of Sports Nutrition · DOI 10.1186/s12970-016-0117-z · source
  19. Schierbauer et al. — 2025Effects of L-citrulline supplementation on exercise capacity in healthy young adults — Frontiers in Sports and Active Living · DOI 10.3389/fspor.2025.1627743 · source
  20. Gough, Sheeran, Shave, Waldron, Jeffries — 2021A critical review of citrulline malate supplementation and exercise performance — European Journal of Applied Physiology · DOI 10.1007/s00421-021-04774-6 · PMID 34417006 · source
  21. Trexler, Smith-Ryan, Stout et al. — 2015International Society of Sports Nutrition position stand: Beta-Alanine — Journal of the International Society of Sports Nutrition · DOI 10.1186/s12970-015-0090-y · PMID 26175657 · source
  22. Solis, Cooper, Hobson et al. — 2015Effects of beta-alanine supplementation on brain homocarnosine/carnosine signal and cognitive function: an exploratory study — PLOS ONE · DOI 10.1371/journal.pone.0123857 · PMID 25875656 · source
  23. Ostfeld, Ben-Zeev, Zamir et al. — 2023Effect of Beta-Alanine Supplementation on Cognitive Function in Older Adults — Nutrients, volume 15 · DOI 10.3390/nu15040923 · PMID 36839281 · source
  24. Shafqat — 2016The effect of L-citrulline supplementation on mood and cognition — a postgraduate thesis, not a peer-reviewed trial — Queen Margaret University eResearch · source
  25. Ambrogi et al. — 2023A New Challenge for the Old Excipient Calcium Carbonate — Pharmaceutics · DOI 10.3390/pharmaceutics15010300 · source
  26. National Institute of Standards and TechnologyArginine — C6H14N4O2, 174.2010 g/mol — NIST Chemistry WebBook · source
  27. National Institute of Standards and Technology2-Oxopentanedioic acid — C5H6O5, 146.0981 g/mol — NIST Chemistry WebBook · source
  28. National Institute of Standards and TechnologyCitrulline — C6H13N3O3, 175.1857 g/mol — NIST Chemistry WebBook · source
  29. National Institute of Standards and TechnologyHydrogen chloride — ClH, 36.461 g/mol — NIST Chemistry WebBook · source
  30. National Institute of Standards and TechnologyMalic acid — C4H6O5, 134.0874 g/mol — NIST Chemistry WebBook · source
  31. National Institute of Standards and Technologybeta-Alanine — C3H7NO2, 89.0932 g/mol — NIST Chemistry WebBook · source
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Who made and checked this VapoCept page

Written byVapoCept Editorial Deskfor Vapoceptdaily, U.S. stocking partner
Reviewed byDr. Mary CunninghamNeuropsychologist
Revisedthe date moves when the page changes

Written from the seller’s panel, the front of the bottle and the sources cited on the page, then reviewed before publication. It is general information for adults and does not replace a conversation with your own clinician.

If your memory or concentration is changing, or you are on medicine for blood pressure or the heart, the first conversation is with your clinician, before the first VapoCept capsule.

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VapoCept — 30 capsules, 30 days665.5 mg declared, 7 names · from $49 a bottleSee the packs