How to compare supplements by cost per dose of the active ingredient

To compare supplements by cost per dose, divide what you actually pay (bundle price plus shipping) by the days of supply, then ask how many milligrams of the ingredient you care about are in each day's serving, and how that compares with the amount used in the study behind the marketing. A cheap daily price means little if the dose is a small fraction of the studied one, and the math cannot be done at all when the label hides the amounts.

Below are the formula and four worked examples taken from reviews on this site. The numbers come from each offer's own price table and label as recorded in our reviews, plus published studies we opened.

Why does price per bottle mislead?

Because a bottle is not a unit of anything. Two bottles can hold different numbers of capsules, different serving sizes and different amounts of the same ingredient. Sales pages also push the biggest bundle by showing a low price per bottle, which hides the cash you pay up front and the shipping on smaller orders.

What you can compare is a cost per day, and, when the label allows it, a cost per milligram of the ingredient doing the work. The second number is only useful when you also know the dose that research used. Nothing here tells you that any dose will work for you: that is a question for a doctor or pharmacist, not a price calculator.

What is the three-step formula?

1. Cost per day = total paid divided by days of supply. Total paid includes shipping and any fee at checkout. Days of supply comes from the serving instructions, not from the bundle name.
2. Ingredient per day = amount per serving times servings per day. Use the Supplement Facts panel, not the marketing copy.
3. Compare with the studied dose. Find the dose used in a human trial of that ingredient, note how long it ran and who took part, and divide the label amount by it.

Step three is where most offers fall apart, and step two is where some never start, because they do not print the amount.

Worked example 1: the one-bottle shipping trap

The Cardio Shield review records these prices for a 30-day bottle (two capsules a day):

Bundle	Total paid	Days	Cost per day
1 bottle, plus $19.95 shipping	$78.95	30	$2.63
3 bottles, free shipping	$147	90	$1.63
6 bottles, free shipping	$234	180	$1.30

The advertised $59 for one bottle becomes $2.63 a day once shipping is added, twice the six-bottle rate. That does not mean the six-bottle bundle is a good deal. It means you are paying for 180 days of a product you have not yet tried, and the refund window is what protects you. The review lists 180 days.

The same page also shows the second problem. Six plant ingredients share one 570 mg proprietary blend, so you cannot work out the cost of any single one. The FDA's labeling guide requires a blend to show its total weight, and Cardio Shield does. It does not have to show individual weights, so you can price the blend as a whole, but not hawthorn, garlic or hibiscus.

Worked example 2: when the whole scoop is smaller than the studied dose

VenoPlus 8 is a powder with a 5.4 g scoop and 30 servings per jar. Prices from the review: $59 for one jar, $147 for three, $234 for six. That is $1.97, $1.63 and $1.30 per scoop.

The review notes that the page gives no amount for any of its ten ingredients, including L-arginine and L-citrulline. We can still do one useful check. A randomized, double-blind, placebo-controlled trial of L-arginine in men with vasculogenic erectile dysfunction used 6 g a day for 3 months in 98 patients (51 on arginine, 47 on placebo), according to its PubMed abstract. The entire VenoPlus scoop weighs 5.4 g before it is divided among ten ingredients, so it cannot contain that dose of arginine alone.

Nitric Boost has the same issue in a different jar. Per its review, it sells a powder with eight ingredients and no amounts, and the page's own centerpiece study used 6 g of L-arginine alone. You can read the Nitric Boost review for the details. At $69 for one jar and $294 for six, the daily cost is $2.30 and $1.63, but the cost per studied dose cannot be calculated, because the label never says what is in a scoop.

Worked example 3: citrulline inside a subscription

The FLOW Nitric Oxide Booster review describes a capsule offer where the first bottle is free (you pay shipping), after which a subscription bills $22.47 to $27.42 a month. A bottle is 30 days, so that is roughly $0.75 to $0.91 a day.

The company's own cited study, a single-blind trial in 24 men with mild erectile dysfunction, gave 1.5 g of L-citrulline a day for one month (PubMed, Cormio et al., Urology, 2011). FLOW's label lists one 850 mg proprietary blend per two-capsule serving, shared by four ingredients. Take the best case, where the entire blend is citrulline, which it is not:

• 1,500 mg divided by 850 mg is about 1.76 servings a day.
• At $0.75 to $0.91 per serving, that is about $1.32 to $1.61 a day.
• A 30-serving bottle would last about 17 days instead of 30.

Because three other ingredients share the blend, the true figures are worse than this floor. The point is not that the product is a bad idea. It is that the "free bottle" and the monthly price are not the cost of the studied dose, and the label does not let you find that cost.

Worked example 4: a complete label, and a small fraction of the research dose

Most offers in this niche hide amounts. Longevity Activator does the opposite and prints a milligram amount for all 14 ingredients, which makes it a fair test of the method. Its review lists 25 mg of fisetin per capsule, one capsule a day. Bundle prices are $118 for 2 bottles plus $9.95 shipping, $147 for 3 bottles plus $9.95, and $198 for 6 bottles with free US shipping, each bottle holding 30 capsules.

• 2 bottles: $127.95 over 60 days is about $2.13 a day.
• 3 bottles: $156.95 over 90 days is about $1.74 a day.
• 6 bottles: $198 over 180 days is $1.10 a day, or about $0.044 per milligram of fisetin.

Now the comparison. The published protocol for a phase 2 trial in elderly sepsis patients specifies fisetin at 20 mg per kilogram of body weight, as a single oral dose or two doses a day apart (Trials, 2024). For a 70 kg adult, that is 1,400 mg, and 25 mg is under 2 percent of it. Matching it with these capsules would take 56 of them, or about $61.60 at the six-bottle price, for one dose.

This is arithmetic, not a recommendation. That protocol is a study design in a hospital setting, not a plan for a supplement user, and the review makes the same point: the label's small daily amount and the research's large intermittent dose are different strategies.

When is cost per milligram the wrong tool?

Cost per milligram only helps when two conditions hold: the amount is printed and a human study supports a particular dose. If either fails, the number misleads.

• The amount is hidden. The MemoVolt, CitrusBurn, Ignitra and AppaNail reviews each record zero disclosed doses, across 10, 7, 6 and 17 named ingredients respectively. You can price a day of each, but not a milligram of anything.
• The amount is printed but nothing supports it. The Arteris Plus review notes that its label shows exact amounts for five herbs, which is more than most offers do, yet it found no clinical trials tying two of those herbs to blood pressure. A cheap cost per milligram of an herb with no trial dose is still a number without meaning.
• The form differs. A plain powder, a 4:1 extract and a 95 percent standardized extract are not interchangeable milligrams.

In those cases fall back to cost per day and to refund terms, which our review method scores separately from evidence.

What is a quick checklist before you buy?

1. Write down the total at the final order page, including shipping and any pre-checked add-on.
2. Divide by days of supply to get cost per day.
3. Find the Supplement Facts panel. If amounts are missing, treat the offer as impossible to price per dose.
4. Look up the dose in one human study, and note its length and size.
5. Compare the label amount with that dose. If it is far below, ask why the page cites the study.
6. Check the refund window and who handles it, then compare similar offers in the brain and memory category or on the reviews page.

FAQ

How do I calculate the cost per day of a supplement?

Divide the total you pay, including shipping, by the number of days the order lasts. Use the serving instructions to get the days. For example, $234 for six 30-day bottles is $1.30 a day.

Is a higher dose always better value?

No. A higher dose is only useful when research supports it for the purpose you have in mind, and higher doses can raise the chance of side effects or interactions with medicines. Ask a doctor or pharmacist before going above a label dose.

What does a proprietary blend hide?

The FDA's labeling guide requires the blend's name and total weight, with ingredients listed by descending weight. It does not require each ingredient's own amount, so the first ingredients may dominate and the last ones may be tiny.

Can I compare prices when the label has no amounts?

Only per day. Without amounts, cost per milligram is impossible to calculate, so compare daily price, shipping and refund terms instead.

This article is general information, not medical advice. A published study dose is not a recommended dose.