What a salt weight hides
Four of the five amino acid entries on this label declare a salt. Reading past the name is the single most portable habit on this website.
“L-Arginine AKG 2:1, 200 mg” declares the weight of the salt. Only 70.5% of it is arginine, so the entry delivers 140.9 mg.
Across a whole label it adds up: 640 mg of declared amino acid entries here deliver 536 mg of actual amino acid. The other 104 mg is acid.
How to spot one
Read past the amino acid name to whatever follows it. Anything there — HCl, hydrochloride, AKG, alpha-ketoglutarate, malate, citrate, aspartate, fumarate, a ratio like 2:1 — means the declared weight includes something that is not the amino acid.
A bare name usually means the free form, where the declared weight and the substance weight are the same number.
| Entry | Salt? | What the declared weight means |
|---|---|---|
| L-Arginine | No | 200 mg of arginine |
| L-Arginine AKG 2:1 | Yes | 200 mg of a salt, part of it arginine |
| L-Citrulline HCl | Yes | 100 mg of a salt |
| L-Citrulline Malate | Yes | 100 mg of a salt, ratio not stated |
| Beta-Alanine | No | 40 mg of beta-alanine |
Scroll this table sideways →
Three of those five entries name their counter-ion clearly and one — the malate — names it without giving the ratio, which is the case where you cannot finish the calculation.
The arithmetic, which is one division
The fraction of a salt that is the amino acid is fixed by chemistry, not by the manufacturer. For a one-to-one salt it is the amino acid's molecular weight divided by the sum of both molecular weights.
You need two numbers, and the NIST Chemistry WebBook has both for free. L-arginine is 174.2010 g/mol. Alpha-ketoglutaric acid is 146.0981 g/mol.
For a 2:1 salt, double the amino acid first. Two arginines weigh 348.402; add one alpha-ketoglutarate and the salt weighs 494.500; arginine is 348.402 ÷ 494.500 = 70.46%.
Multiply the declared amount by that fraction and you have what you are getting. 200 mg × 0.7046 = 140.9 mg.
The 2:1 is checkable, not a marketing flourish
PubChem's entry for L-arginine alpha-ketoglutarate 2:1, CID 76045315, carries the formula C17H34N8O9 — exactly two arginines plus one alpha-ketoglutarate. A separate entry covers the 1:1 salt, which is a different compound.
The common salts, converted
These are the conversions that come up most often on amino acid labels, all calculated from NIST molecular weights.
| Salt | Fraction that is the amino acid | 1,000 mg gives you |
|---|---|---|
| L-Arginine HCl | 82.7% | 827 mg arginine |
| L-Arginine AKG 2:1 | 70.5% | 705 mg arginine |
| L-Citrulline HCl | 82.8% | 828 mg citrulline |
| L-Citrulline Malate 2:1 | 72.3% | 723 mg citrulline |
| L-Citrulline Malate 1:1 | 56.6% | 566 mg citrulline |
Scroll this table sideways →
The last two rows are the interesting pair. The same product name, two different ratios, and a 157 mg difference per gram — which is why a label that does not state its ratio has not really told you what is in it.
A 2021 critical review reports NMR analysis finding that many citrulline malate manufacturers miss their stated ratio, with most landing near 1.6:1 and some as low as 1.1:1. So even a stated ratio is not always the ratio.
Why labels do it
It would be easy to read salt declarations as deliberate inflation. Sometimes they are. Often they are not, and the honest reasons matter.
- It is what the manufacturer bought. The raw material is purchased, weighed and blended as a salt, so the salt weight is the figure that exists in the batch record.
- Salts are more stable. Free-base amino acids can be hygroscopic; a hydrochloride is usually easier to handle and store.
- Some salts absorb differently, which is the real argument for citrulline malate over plain citrulline.
- The counter-ion sometimes does something of its own. Malate enters the citric acid cycle; alpha-ketoglutarate has its own literature.
- Nothing requires disclosure. A label reporting salt weight is compliant, so 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 how it thinks about its buyer.
The counter-ion sometimes does something
So far this post has treated the non-amino-acid part of a salt as dead weight. That is the right default and it is not always true, and being fair about the exceptions makes the rule more useful.
- Hydrochloride
- Chloride. Physiologically ordinary and present in the diet in grams. Genuinely inert at these amounts — this one really is just weight.
- Malate
- Malic acid enters the citric acid cycle. Whether that contributes anything at supplement doses is contested, and it is the usual argument for citrulline malate over plain citrulline in exercise products.
- Alpha-ketoglutarate
- Also a citric acid cycle intermediate, and it has a literature of its own in nitrogen metabolism. Whether it adds anything alongside arginine is not something we found a clean answer to.
- Citrate, aspartate, fumarate
- All metabolically active molecules in their own right, all present at amounts far below where anyone studies them in a typical supplement.
So the honest position is not “the counter-ion is worthless”. It is that the counter-ion is a separate substance with its own evidence and its own dose question, and lumping it into the amino acid's declared weight answers neither.
A label that wanted credit for the malate would say how much malate is in there and what it is for. None of them do, which tells you the counter-ion is being carried for stability and manufacturing rather than for effect.
What good disclosure looks like
A minority of labels do this properly, and they are recognisable at a glance. It is worth knowing what to look for, because it is a fast proxy for how a company thinks about its buyer.
| Declaration | What it tells you |
|---|---|
| L-Arginine HCl 1,000 mg | The salt weight only. You do the conversion or you do not know |
| L-Arginine HCl 1,000 mg (providing 827 mg L-arginine) | Both figures. Nothing to calculate and nothing to hide |
| L-Arginine (as L-Arginine HCl) 827 mg | The base weight, with the form named. The clearest of the three |
Scroll this table sideways →
The second and third forms cost a manufacturer nothing except a slightly smaller-looking number on the panel, which is exactly why they are rare. A company willing to print the smaller number is telling you something.
None of the five amino acid entries on the label this post was written about uses either of the clearer forms. That is the industry norm rather than an outlier, and the conversion is yours to do.
One more place to check
Multivitamins do the same thing with minerals, and there the stakes are higher because Daily Values are involved. “Magnesium oxide 400 mg” is about 60% elemental magnesium; magnesium citrate is around 16%. Two products declaring 400 mg can differ nearly fourfold in what they deliver.
Doing it yourself, once
If you take one habit from this post, make it this one, and do it once on something you already own.
- Pick a product in your cupboard with an amino acid or a mineral on the panel.
- Read past the name to the form in brackets or after it.
- Search the NIST Chemistry WebBook for both molecular weights — the substance and the counter-ion.
- Divide the substance's weight by the sum, remembering to double the substance first if the ratio is 2:1.
- Multiply the declared amount by that fraction.
- Compare the result against what you thought you were buying.
Most people find the gap smaller than they feared and larger than they expected, which is about the right reaction. It is rarely the thing that decides whether a product is worth buying, and it is always worth knowing.
And once you have done it once, you will never read an amino acid panel the same way again, which is the actual point of the exercise.
A closing caution about this check
It is worth ending where the long version ends: this is a skill, not a scandal. On most labels the salt arithmetic moves the figure by ten to twenty per cent, which changes a comparison and rarely changes a verdict on its own.
Where it earns its keep is between two products on the same shelf at the same price. There, ten per cent is the whole difference, and it is hidden in a footnote neither label prints.
When it actually matters
It is worth being honest about how much weight this check carries.
On the label it was worked out for, the salt arithmetic costs about 104 mg out of 640 mg — roughly 16%. That is real and it is not what decides anything there, because the amino acids on that label are ten to sixty times below their studied doses whichever way you count them.
Where it decides things is in a straight comparison. Two arginine products at $30, one declaring 1,000 mg of the hydrochloride and one declaring 1,000 mg of the free base. The second gives you 21% more arginine for the same money, and neither label prints that.
So this is a skill worth two minutes rather than a scandal worth an article. Read past the name, look up two molecular weights, divide. It works on every pre-workout, every amino blend and every nitric oxide product on the shelf.
The long version →Where it fits in the method →What it feeds →
Who made and checked this VapoCept page
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.