How to Read a Supplement Label: DRI, MGO and What the Numbers Mean

Most supplement decisions are made from the front of the pack, which is the part designed to sell rather than to inform. Almost everything you need to compare two products properly is on the back, in smaller type. Here is how to read it.

1. Find the elemental amount, not the compound weight

This is the single most common way shoppers are misled — usually legally.

"Magnesium citrate 500 mg" and "magnesium 500 mg" mean completely different things. The first is the weight of the whole compound, of which magnesium is a fraction. Magnesium citrate is roughly 16% elemental magnesium; magnesium oxide is roughly 60%. So 500 mg of citrate delivers around 80 mg of magnesium, while 500 mg of oxide delivers around 300 mg — though the oxide is absorbed far less well, which is a separate issue.

The same applies to zinc, iron, calcium and every other mineral. Look for the line that names the nutrient alone, usually with a percentage beside it.

2. %DRI or %NRV is your comparison tool

DRI (Dietary Reference Intake) and NRV (Nutrient Reference Value) express the amount as a percentage of an EU reference figure for adults. This is what makes two differently formulated products comparable at a glance.

A few things worth knowing:

• It is a single adult reference, not personalised — requirements differ by age, sex, pregnancy and health status.
• Not every nutrient has an NRV. Ingredients like collagen, Q10, probiotics and botanical extracts have none, which is why they show only milligrams.
• Percentages well above 100% are not automatically wrong — but they are worth noticing, especially for vitamin A, vitamin D, iron, zinc and selenium.

3. Check the serving size before comparing price

"90 capsules" tells you nothing until you know how many make a daily serving. A 90-capsule bottle at three capsules a day is a 30-day supply. A 90-tablet bottle at one a day is a 90-day supply. Divide price by daily servings, never by unit count.

This is also where dose splitting hides. A product showing an impressive nutrient panel "per 3 capsules" is a different proposition from one delivering the same per single tablet.

4. Read the ingredient order

Ingredients appear in descending order of weight. In a blend of magnesium forms, whichever appears first dominates — so a product listing oxide first is essentially an oxide product regardless of what follows.

Also scan for fillers, bulking agents and capsule material. Hypromellose indicates a vegetarian or vegan capsule; gelatin does not. This is where you find out whether "plant-based" applies to the whole product or only the contents.

5. Understand which claims are legally regulated

In the EU, a supplement may only make health claims from an authorised list, worded carefully. "Magnesium contributes to normal muscle function" is authorised. "Magnesium relieves cramp" is not. "Supports immunity" is vaguer than the authorised "contributes to the normal function of the immune system" and often signals a product cutting corners.

Meanwhile, these terms are not regulated and tell you little on their own:

• Superfood — marketing category, no legal definition
• Clinically proven — without a citation, unverifiable
• Natural — no legal threshold for supplements
• Pharmaceutical grade — means nothing for a food supplement
• Bioavailable — sometimes meaningful, but never quantified on a label

6. Special cases worth knowing

MGO on manuka honey

MGO measures methylglyoxal in mg/kg. MGO 250 and MGO 400 are concentration grades, not medical ratings — a higher number means more methylglyoxal and a higher price, nothing more. UMF is an alternative scale you may see. Honey is not suitable for infants under 12 months.

CFU on probiotics

Colony Forming Units count viable bacteria. The number that matters is CFU at end of shelf life, not at manufacture — they are very different figures and only the first is useful. Also look for full strain names: Lactobacillus rhamnosus GG, not just "Lactobacillus", because effects are strain-specific.

IU versus µg on vitamins

Vitamins A, D and E appear in both units. For vitamin D, 1 µg = 40 IU, so 1000 IU = 25 µg. "mcg" and "µg" are the same thing. See our vitamin D guide for the full conversion table.

Extract ratios on botanicals

"10:1 extract" means ten parts raw material produced one part extract. More useful is a standardised marker — "withanolides 5%" for ashwagandha, "curcuminoids 95%" for turmeric — because that tells you what is actually in it rather than how much was boiled down.

7. Read the warnings, genuinely

The small print is where the real safety information lives: pregnancy and breastfeeding cautions, age limits, medication interactions, allergens, and the maximum daily amount. Some are legally required and some are the manufacturer flagging something specific. Iron warnings about keeping products away from children are not boilerplate — iron overdose is a leading cause of serious poisoning in young children.

A three-question shortcut

1. How much of the actual nutrient, per daily serving? Find the elemental figure and the %DRI.
2. How many days does the pack last, and what does a day cost? Price ÷ daily servings.
3. What form is it, and does that form matter here? For minerals, often yes. For vitamin C, rarely.

If a product will not let you answer those three from the label, that is itself informative.

Food supplements should not replace a varied, balanced diet and a healthy lifestyle. Always read the product label and follow the stated directions. This article is general information, not medical advice. Seek advice from a doctor or pharmacist before supplementing during pregnancy or breastfeeding, alongside prescription medication, or when managing a medical condition.