A dose is four numbers, not one

In Lesson 01, dose was the first of three checks. Here's the catch: the number printed on the front of the jar is only one part of a dose. When a trial reports that something worked, it used a full protocol, and you only get the trial's result if you copy the whole thing.

A dose is amount times frequency times duration, scaled to body weight Four tiles joined by multiplication signs, using creatine as the example: 3 to 5 grams per serving, once a day, for four or more weeks, roughly 0.03 grams per kilogram of body weight. EXAMPLE · CREATINE MONOHYDRATE, AS STUDIED × × × AMOUNT 3–5 g per serving FREQUENCY daily not "now and then" DURATION 4+ weeks to fill muscle stores SCALED TO YOU ≈0.03 g/kg of body weight
Change any one tile and you're running a different experiment. Creatine's maintenance dose is about 3–5 g a day, or roughly 0.03 g per kg of body weight.1 Five grams taken twice a week isn't a smaller version of that protocol. It's a protocol nobody tested.
  • Amount — how much per serving. Always check what a "serving" is first: one capsule, or three? (Path 01 covers per-serving tricks.)
  • Frequency — once a day, split through the day, alternate days, or only before training.
  • Duration — how long before the effect appears. Some things act within an hour, and others need weeks of build-up.
  • Scaling — whether the dose is fixed or should scale with body weight. Many sports supplements are studied in mg per kg.

Where the "studied dose" actually comes from

The best answer is rarely one trial. In rough order of trust, look for:

  1. Position stands and meta-analyses, which summarise the dose range across many trials. Sports nutrition societies publish these for creatine, caffeine and beta-alanine.
  2. Government fact sheets, like the NIH Office of Dietary Supplements, for vitamins and minerals: requirements, upper limits, and the doses used in research.
  3. The individual trial a brand cites, read for its exact protocol, not just its conclusion.

Then ask two follow-up questions:

  • A dose of what? "600 mg ashwagandha" from a standardised root extract and 600 mg of plain root powder are different products. The studied dose belongs to the studied material (see KSM-66 vs Sensoril).
  • Studied in whom? Results from deficient people don't automatically apply to replete ones, and vice versa. The iron-dosing research below was done in young women who were iron-depleted.2 Athletes, older adults and people on medication can each respond differently.

The four shapes of "more"

"How much is enough?" depends on how the response curve bends. Most supplements follow one of four shapes, and each one tells you something different about the bigger number on the shelf.

Four shapes of dose-response: plateau, threshold, U-shaped and capped Four small charts. Plateau: benefit rises then flattens. Threshold: nothing happens until a store fills, then benefit rises. U-shaped: risk is high at very low and very high doses. Capped: the amount absorbed stops rising after a point. Plateau — benefit levels off e.g. caffeine, melatonin EFFECT DOSE → Threshold — nothing until stores fill e.g. beta-alanine, creatine EFFECT DOSE → U-shaped — too little and too much hurt e.g. vitamin B6, vitamin D, zinc RISK DOSE → Capped — absorption tops out e.g. vitamin B12, iron ABSORBED DOSE →
Schematic shapes, not data. Before you reach for a bigger number, ask which shape the ingredient follows. Only a threshold-type supplement is clearly hurt by too small a dose. For the other three, extra milligrams buy little or nothing, or bring a different risk.
  • Plateau. Benefit rises, then flattens. For caffeine, 3–6 mg per kg improves performance, while very high doses (around 9 mg/kg) mostly add side effects.3 Past the plateau, you're paying for side effects.
  • Threshold. Nothing much happens until a store fills up. Beta-alanine needs about 4–6 g a day for at least 2–4 weeks to raise muscle carnosine enough to matter.4 A pre-workout with 1.5 g, taken only on gym days, never reaches that threshold.
  • U-shaped. Too little is a problem, and too much is a different problem. Vitamin B6 is essential, but long-term high intake is linked to peripheral nerve damage.5 Many vitamins and minerals sit on a U.
  • Capped. The body limits how much it takes in. B12's carrier saturates at about 1–2 mcg per dose.6 With iron, doses of 60 mg or more raise hepcidin and cut the next day's absorption.2 Taking more on the same day mostly gets wasted.

Body weight: the quiet mismatch

Fixed-dose products assume an average body. Many sports trials report doses in mg per kg, and a single scoop means very different things for a 50 kg and a 90 kg person. Caffeine shows it best:

The same caffeine scoop is a different dose at different body weights Chart of caffeine milligrams against body weight from 45 to 95 kilograms. A shaded band shows the 3 to 6 milligram per kilogram range. A 300 milligram scoop sits at the top of the band for a 50 kilogram person; a 200 milligram scoop sits below the band for a 90 kilogram person. 9 mg/kg — side effects common 200 mg scoop 300 mg scoop 3–6 MG/KG BAND 50 kg: 300 mg = 6 mg/kg 90 kg: 200 mg = 2.2 mg/kg 50 60 70 80 90 BODY WEIGHT (KG) → 0 200 400 600 CAFFEINE (MG)
One scoop, two very different doses. The shaded band is the 3–6 mg/kg range linked to performance benefits.3 A 300 mg scoop already hits the top of the band for a 50 kg lifter, before any chai or coffee that day. A 200 mg scoop sits below the band for a 90 kg one, though doses as low as 2 mg/kg may still help.

To convert, divide the dose by your weight in kg. Then add up every source for the day. For caffeine that means tea, coffee and soft drinks too (see caffeine tolerance and chai).

Duration and frequency: the parts nobody prints

Labels almost never say how long a dose takes to work or how to space it. Trials often answer both, and sometimes the answer is surprising.

Creatine loading reaches the same muscle level faster, not higher Two lines show the rise in muscle creatine over 30 days. Loading at 20 grams a day reaches about a 20 percent increase by day 6. Taking 3 grams a day reaches the same 20 percent by day 28. Both lines then stay level. +20% 0 20 g/day loading day 6: stores full 3 g/day, no loading day 28: same level 0 6 15 28 DAYS → MUSCLE CREATINE ↑
Loading buys speed, not size. In the classic study, 20 g a day for 6 days and 3 g a day for 28 days both raised muscle creatine by about 20%.7 The curves are smoothed for illustration. (More in should you load creatine?)

Frequency can matter just as much. In iron-depleted women, 60 mg of iron on alternate days led to a larger share of each dose being absorbed than the same dose on consecutive days, and splitting it into twice-daily doses didn't help.8 The "obvious" schedule, a pill every day or two a day for a stronger effect, turned out to be the less efficient one. The same logic applies to weekly 60,000 IU vitamin D sachets. The weekly total may look like a daily dose times seven, but the body doesn't treat them as the same.

Upper limits: where "more" becomes risk

For vitamins and minerals, expert bodies set a Tolerable Upper Intake Level (UL): the most you can take daily, long term, from all sources combined, without expecting harm. Three you'll meet often:

  • Vitamin D: 4,000 IU (100 mcg) a day for adults.9
  • Zinc: 40 mg a day for adults.10 Long-term intake above that can interfere with copper.
  • Vitamin B6: 100 mg a day under the US limit.11 In 2023, Europe's food-safety authority set a much lower adult UL of 12 mg a day, based on nerve-damage reports.5 Two agencies, an eight-fold difference. When they disagree, we'd stay under the lower one unless a doctor says otherwise.
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The UL counts everything — and it isn't a target

Upper limits apply to your total intake: food, fortified products and every supplement combined. A multivitamin plus a "hair, skin & nails" gummy plus a B-complex can quietly stack the same nutrient three times. Path 01 shows how to find hidden duplicates. Doses above the UL are sometimes prescribed on purpose, for example to correct a diagnosed deficiency. That's a short course under medical supervision, not something to copy from a label.

Worked example: a 30-second dose audit

Worked example A 55 kg lifter's pre-workout + multivitamin (composite labels)
PRE-WORKOUT · Serving: 1 scoop (12 g) Caffeine Anhydrous ........................ 300 mg Beta-Alanine ............................. 1.6 g Creatine Monohydrate ...................... 1 g MULTIVITAMIN · Serving: 1 tablet Vitamin B6 (as Pyridoxine HCl) ............ 50 mg Zinc (as Zinc Oxide) ...................... 25 mg + separate zinc tablet, 20 mg

These are illustrative composites, not real products. Here's how each line holds up for someone who weighs 55 kg:

Caffeine 300 mg → 5.5 mg/kg. Within the 3–6 mg/kg range, but near the top before counting a single cup of chai. Half a scoop may give most of the benefit with fewer jitters.

Beta-alanine 1.6 g → below the threshold. The studied intake is 4–6 g a day, taken daily, for weeks. At 1.6 g only on training days, it never gets there. The tingle you feel is not proof it's working.

Creatine 1 g → under-dosed. About a third of the 3–5 g maintenance dose. Plain creatine monohydrate at the right dose is cheaper than paying for 1 g inside a pre-workout.

B6 50 mg → above the EU upper limit of 12 mg, though under the US limit of 100 mg. Taken daily for months, that's the kind of intake linked to nerve symptoms.

Zinc 25 + 20 = 45 mg → over the 40 mg UL. Neither product is over on its own, but together they are. This is the stacking problem.

Studied doses at a glance

IngredientStudied doseFrequency & durationWatch out for
Creatine monohydrate 3–5 g/day (≈0.03 g/kg)1 Daily; ~4 weeks to saturate, or ~6 days with loading7 1–2 g "sprinkles" in blends
Caffeine 3–6 mg/kg3 Usually ~60 min before exercise Fixed 300 mg+ scoops for light lifters; hidden caffeine in other drinks
Beta-alanine 4–6 g/day4 Daily for ≥2–4 weeks; split doses reduce tingling 1–2 g per scoop, taken only on gym days
Melatonin 0.3–1 mg (details) Before bed, timed to your sleep 5–10 mg tablets
Iron Set by a doctor for deficiency Alternate-day single doses absorbed better than daily or split doses8 ≥60 mg raises hepcidin2; don't self-treat without a blood test
Vitamin D UL 4,000 IU/day9 Daily vs weekly isn't equivalent Stacking a sachet + multivitamin + fortified foods
Zinc UL 40 mg/day10 Long-term high intake affects copper Multivitamin + standalone zinc + ZMA
Vitamin B6 UL 100 mg (US)11 / 12 mg (EU)5 Risk builds with months of daily use B-complex and "energy" products with 25–100 mg

Frequently asked questions

How do I find the right dose for a supplement?

Look for the dose range used across trials, not just one study. Position stands, meta-analyses and government fact sheets (such as the NIH Office of Dietary Supplements) are the best starting points. Then match the whole protocol — amount, frequency, duration and, where relevant, mg per kg of body weight — and the exact form or extract that was tested.

Is taking a higher dose of a supplement more effective?

Usually not. Many supplements plateau, so extra amounts add side effects rather than benefit. Some have absorption caps, so the extra is never taken in. Vitamins and minerals often follow a U-shaped curve, where too much causes its own harm. Only for threshold-type supplements, like beta-alanine, does a dose that's too low mean you get nothing.

What is a tolerable upper intake level (UL)?

The UL is the highest daily intake, from food and all supplements combined, that is unlikely to cause harm over the long term. Examples for adults: vitamin D 4,000 IU, zinc 40 mg, and vitamin B6 100 mg in the US or 12 mg in the EU. It is a ceiling, not a target.

Should supplement doses depend on body weight?

For many sports supplements, yes. Caffeine is studied at 3–6 mg per kg, so a 300 mg scoop is about 6 mg/kg for a 50 kg person but only about 3.3 mg/kg for a 90 kg person. Divide the dose by your weight in kg to see where you land.

What to remember

Copy the whole protocol, not just the milligrams.

  • A dose is four numbers: amount, frequency, duration, and (often) mg per kg. Change one and the trial result no longer applies cleanly.
  • Know the curve's shape. Plateau, threshold, U-shaped or capped tells you whether more helps, does nothing, or harms.
  • Upper limits count everything. Add up every product and fortified food, and treat the UL as a ceiling. When agencies disagree, the lower limit is the cautious choice.
Try it · ~3 min

Audit one product you take every day.

  1. Find the serving and write the dose per serving for the main ingredient.
  2. Look up the studied range (our ingredient pages list it). Note frequency and duration as well as amount, and divide by your weight if it's a mg/kg ingredient.
  3. Add up duplicates across everything you take for the same nutrient, and check the total against its UL.

Goes deeper

ResearchShould you really "load" creatine? A look at 27 trials ResearchWhy India's 10 mg melatonin tablets get the dose wrong ResearchPre-workout proprietary blends in India ResearchZMA — what the zinc and magnesium evidence shows LessonClaims language — what "clinically dosed" means

References

1
Kreider RB, Kalman DS, Antonio J, et al. International Society of Sports Nutrition position stand: safety and efficacy of creatine supplementation in exercise, sport, and medicine. J Int Soc Sports Nutr. 2017;14:18. doi:10.1186/s12970-017-0173-z
2
Moretti D, Goede JS, Zeder C, et al. Oral iron supplements increase hepcidin and decrease iron absorption from daily or twice-daily doses in iron-depleted young women. Blood. 2015;126(17):1981–1989. doi:10.1182/blood-2015-05-642223
3
Guest NS, VanDusseldorp TA, Nelson MT, et al. International society of sports nutrition position stand: caffeine and exercise performance. J Int Soc Sports Nutr. 2021;18(1):1. doi:10.1186/s12970-020-00383-4
4
Trexler ET, Smith-Ryan AE, Stout JR, et al. International society of sports nutrition position stand: Beta-Alanine. J Int Soc Sports Nutr. 2015;12:30. doi:10.1186/s12970-015-0090-y
5
EFSA Panel on Nutrition, Novel Foods and Food Allergens (NDA). Scientific opinion on the tolerable upper intake level for vitamin B6. EFSA Journal. 2023;21(5):8006. doi:10.2903/j.efsa.2023.8006
6
NIH Office of Dietary Supplements. Vitamin B12 — Fact Sheet for Health Professionals. ods.od.nih.gov
7
Hultman E, Söderlund K, Timmons JA, Cederblad G, Greenhaff PL. Muscle creatine loading in men. J Appl Physiol. 1996;81(1):232–237. doi:10.1152/jappl.1996.81.1.232
8
Stoffel NU, Cercamondi CI, Brittenham G, et al. Iron absorption from oral iron supplements given on consecutive versus alternate days and as single morning doses versus twice-daily split dosing in iron-depleted women: two open-label, randomised controlled trials. Lancet Haematol. 2017;4(11):e524–e533. doi:10.1016/S2352-3026(17)30182-5
9
NIH Office of Dietary Supplements. Vitamin D — Fact Sheet for Health Professionals. ods.od.nih.gov
10
NIH Office of Dietary Supplements. Zinc — Fact Sheet for Health Professionals. ods.od.nih.gov
11
NIH Office of Dietary Supplements. Vitamin B6 — Fact Sheet for Health Professionals. ods.od.nih.gov

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