How to Read a Supplement Label

Two bottles of "magnesium" can contain very different amounts. Two products with the same name can be very different quality. The label is where you find out. Here is what to check.

1. Serving size comes first

Everything on the panel is per serving, and a serving is often more than one capsule. If the serving is "2 capsules" and the panel says 200 mg, one capsule is only 100 mg. Always check how many you are actually taking.

2. Look at the amount, not the name

A product can say "Magnesium 500 mg" on the front and contain far less elemental magnesium, which is the part your body uses. Check whether the amount is listed as:

• elemental magnesium (what counts), or
• the compound (for example magnesium citrate 500 mg, which may only contain about 80 mg of elemental magnesium)

The same is true for calcium, zinc, iron and others.

3. Watch the units

• mg (milligram) and mcg (microgram) differ by a factor of 1,000. 1 mg = 1,000 mcg.
• IU is used for some vitamins. For vitamin D, 40 IU = 1 mcg, so 1,000 IU = 25 mcg.

Mixing these up is a common reason people take far too much or too little.

4. Be wary of "proprietary blends"

A "proprietary blend" lists the total weight but not the amount of each ingredient. You cannot tell if the key ingredient is there at a useful dose. Prefer products that show each amount.

5. Check the form of the nutrient

Different forms behave differently. For example, vitamin B12 may be methylcobalamin or cyanocobalamin, and magnesium may be glycinate, citrate or oxide. A brand is not automatically better because the form sounds fancy. What matters is the amount and what suits you.

6. Read "Other ingredients"

This lists fillers, sweeteners, colours and allergens such as soy, milk, gluten or shellfish. If you have allergies or follow a halal or vegetarian diet, check the capsule material too.

7. Be careful with marketing claims

"Natural", "pure", "clinically proven" and "doctor recommended" are not guarantees. Be cautious of any product that claims to cure, treat or prevent a disease.

8. Quality seals and registration

• Third-party testing seals (such as USP or NSF) mean an independent group checked that the product contains what it says and is free of certain contaminants. They do not prove the supplement works.
• In Malaysia, registered health supplements carry a registration number (starting with "MAL") on the label. You can check that number on the NPRA Quest3+ product search. A product with no number, or a number that does not check out, is a warning sign.
• Check the expiry date and storage instructions.

9. Check the dose against safe limits

If you take more than one product, add up what you take across all of them. This matters most for vitamin A, vitamin D, iron, zinc and magnesium.

10. When in doubt, ask

If you cannot work out what a label means, or it lists something you do not recognise, ask a pharmacist before you buy.

Check your own list

Use the free Interaction Checker on VitaGuide to see whether your medicines and supplements may interact, or email our pharmacist for a review.

---

This article is general information and not medical advice. It does not replace advice from your own doctor or pharmacist.

Sources to verify before publishing: NIH Office of Dietary Supplements guidance on reading supplement labels; NPRA (Malaysia) information on product registration and the Quest3+ system. Please confirm the current NPRA registration number format before publishing.