How to read a supplement label — registration number, %Thai RDI, ingredient forms and warnings

The back of the bottle is the most honest document a supplement has, because every line is set by law rather than by marketing. Here is how to read it.

1. The 13-digit food serial number

Supplements sold in Thailand must show the Thai FDA mark with a 13-digit food serial number, under the Ministry of Public Health notification on dietary supplements [1]. You can check it in the FDA's product verification system [2]. It tells you the product's formula and label were reviewed and permitted — not that it "works", and not that every batch was tested.

2. Ingredient names and amounts

The law requires key ingredients and their amounts in descending order [1]. The common confusion is compound weight versus elemental amount: Zinc Bisglycinate 75 mg provides 15 mg of zinc. Compare the second number — the same convention US labels use, listing elemental amounts rather than whole-molecule weight [3].

3. %Thai RDI

Thai RDI is the recommended daily intake for Thais aged six and over, set in the current nutrition-labelling notification (No. 445, B.E. 2566) [4]. The percentage shows how much of that reference one serving provides. Two caveats: it is a population reference, not your personal need, and more than 100% is not automatically better. Excess water-soluble vitamins are mostly excreted, but some minerals such as selenium are linked to abnormal shedding when taken in excess over time [5].

4. The form of each ingredient

The full name tells you the form — zinc may be sulfate, oxide or bisglycinate, and forms differ in absorption and stomach comfort [3]. Vitamin B3 comes as niacin (nicotinic acid), which can flush, or nicotinamide, which does not. A label that names the form makes it easier for you and your pharmacist to judge.

5. Mandatory warnings

Every supplement must carry a boxed warning with at least three statements: not for children or pregnant women · eat a varied diet from all five food groups regularly · has no effect in preventing or treating disease [1]. These are required of every brand; a bottle without them is the one to question.

6. What a label cannot say

Supplements are not medicines and may not claim to treat, cure or prevent disease, in Thailand [1] or the US [6]. Permitted statements are nutrition claims such as "biotin, zinc and selenium contribute to the maintenance of normal hair". Anything bigger is a warning sign, not a selling point.

30-second checklist

• 13-digit serial number you can verify
• Elemental amounts and %Thai RDI
• Forms, not just names
• Full warning box
• Manufacturer, address, expiry date
• No promises the law does not allow

The U-TURN label lists all 18 nutrients with elemental amounts and %Thai RDI. Biotin, zinc and selenium contribute to the maintenance of normal hair, for people who do not get enough from food each day. One capsule a day with the first meal of the day, or whichever meal suits you · Thai FDA 74-1-01357-5-0197 · Dietary supplement; not intended to prevent or treat any disease.