Units: the decimal points that hide in plain sight

Three weight units cover almost everything on a supplement label, and the gap between them is enormous:

  • g (gram) — for protein, creatine, fibre. The big stuff.
  • mg (milligram) = one-thousandth of a gram. Most actives: caffeine, vitamin C, magnesium.
  • mcg or µg (microgram) = one-thousandth of a milligram. Trace nutrients: B12, vitamin D, folate, chromium, selenium.

The trap is that mg and mcg differ by 1000× and look almost identical in small print. "Vitamin D 1000 mcg" would be a huge, near-toxic dose; the label almost certainly means IU or a far smaller mcg figure. Train your eye to actually read the unit, not just the number — a "500" of vitamin B12 in mcg and a "500" of vitamin C in mg are a thousand-fold apart in scale.

IU — the unit that isn't a weight

Older nutrients (vitamins A, D, E) are often still printed in International Units — a measure of biological activity, not mass. Indian labels lean on IU heavily, especially for vitamin D. The conversions are fixed, and this one ladder covers 90% of what you'll meet:

Vitamin D dose ladder converting International Units to micrograms 400 IU 10 µg supp. floor 600 IU 15 µg adult RDA 1000 IU 25 µg common dose 2000 IU 50 µg daily upper 60000 IU 1500 µg weekly sachet
Vitamin D: 1 IU = 0.025 µg, so 40 IU = 1 µg. The familiar 60,000 IU weekly sachet is 1,500 µg — a deliberately large weekly bolus, not a daily dose. Reading it as "60,000 of something small" is how people take it far too often. Same number, very different meaning once you convert.

%RDA: a percentage of whose day?

"% RDA" (or %RDI / %DV) tells you how much of a day's recommended intake one serving provides. Useful — but two things are quietly assumed:

  • Whose recommendation? In India the reference is the ICMR–NIN Recommended Dietary Allowances (2020) for Indians. A label using US Daily Values can show a different percentage for the exact same amount, because the baseline differs.
  • More than 100% is not "better". "1000% of your daily Vitamin C!" means ten days' worth in one serving. For water-soluble vitamins the excess is mostly excreted; for fat-soluble ones (A, D, E, K) and some minerals, chronic megadoses can actively harm. A big percentage is a marketing flex, not a quality signal.
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The 100% ceiling that isn't there

%RDA has no upper cap on a label, so brands stack eye-catching numbers — 500%, 1667% — that sound generous and cost them almost nothing for cheap vitamins. Treat anything far above 100% as decoration, and for A, D, E, K and iron, as a reason to check the actual dose against the safe upper limit.

The serving-size lever

Here's the most powerful number-bender of all, and it's almost invisible: every "per serving" figure is divided by a serving size the brand chooses. Shrink the serving and every number on the panel — good and bad — shrinks with it. The sugar looks lower, the calories look modest… and you quietly need two servings to get the protein they advertised.

Two habits defuse it entirely:

  • Compare per 100 g, never per serving. Indian labels must also declare values per 100 g / 100 ml. That column is serving-size-proof — use it to compare two products honestly.
  • Check servings-per-container against your real usage. If the tub claims "30 servings" but each is one 30 g scoop and you use two, it's a 15-day tub. The per-gram price doubles, and so does the sugar you actually eat.
Worked example A "high protein" drink mix and the serving it hopes you skim
HIGH-PROTEIN HEALTH MIX Serving size: 2 heaped scoops (40 g) Servings per container: 25 Per serving Per 100 g Energy 152 kcal 380 kcal Protein 10 g 25 g Added sugar 6 g 15 g

The framing: "10 g protein!" sounds solid and the sugar reads as a tidy 6 g — per serving. But the serving is two scoops of 40 g. Most people use one.

Per 100 g tells the truth: it's 25% protein and 15% added sugar — for every 2 g of protein you're taking roughly 1.2 g of sugar. And a "1 kg, 25-serving" tub is really ~12 days if you (reasonably) use one scoop and expect the advertised protein. The per 100 g column ended all of that guesswork in five seconds.

None of these three levers requires the brand to lie. The unit is real, the percentage is real, the serving is real. They're just arranged so the flattering reading is the effortless one. Do the small conversions — IU to µg, salt to element (last lesson), per-serving to per-100 g — and the flattering reading and the true one finally become the same thing.

What to remember

Read the unit, question the percentage, distrust the serving.

  • mg and mcg are 1000× apart and look alike in small print. For A/D/E, convert IU to µg — 40 IU = 1 µg, so 60,000 IU = 1,500 µg.
  • %RDA has no ceiling on a label. Anything far over 100% is a flex, not quality — and for fat-soluble vitamins and iron, a reason to check the safe upper limit.
  • Every "per serving" number is divided by a serving the brand chose. Compare per 100 g instead, and check servings-per-container against how you actually use it.
Try it · ~1 min

Put one label through the three checks.

  1. Pick any nutrient and say its unit out loud — g, mg, or mcg. Is the number sensible for that scale?
  2. Find a %RDA over 100%. Is it a water-soluble vitamin (harmless excess) or a fat-soluble one / mineral (check the upper limit)?
  3. Read the serving size, then re-read every "per serving" figure using the per 100 g column instead. Notice what changes.

Goes deeper

ResearchThe 60,000 IU vitamin D sachet — dose, timing, and the mistakes Lesson 04“Proprietary blend” — what it actually hides

References

1
Indian Council of Medical Research – National Institute of Nutrition. Recommended Dietary Allowances and Estimated Average Requirements for Indians (RDA 2020). nin.res.in
2
NIH Office of Dietary Supplements. Vitamin D — Fact Sheet for Health Professionals (IU-to-microgram conversion; tolerable upper intake). ods.od.nih.gov
3
FSSAI. Food Safety and Standards (Labelling and Display) Regulations, 2020 — mandatory per-100 g / per-serving nutritional declaration.

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