Buying guide · Sources checked 17 October 2026 · Not clinically reviewed
The front of a pack is a starting point. The serving instructions and ingredient panel are where a more useful comparison begins.
Compare the same things
Put the product names aside for a moment. Make a short note of the nutrient amount, the unit used, whether that amount is per tablet or per serving, and the number of tablets or capsules in that serving. Two pack prices are difficult to compare if these details differ.
Units matter. For vitamin D, standard clinical nutrition guidance explains that 1 microgram equals 40 IU. That conversion applies to vitamin D; do not use it as a universal conversion for other nutrients.
Read the full panel
Serving instructions
Find the labelled amount to take and the warnings beside it. Do not change the serving simply to make a pack last longer or compare more favourably.
Ingredients and suitability
Read the ingredient list and any allergy or dietary information. If the information you need is missing, ask the manufacturer or a healthcare professional.
Seller and exact product
Check the strength, format and pack size on the actual listing. A familiar brand name alone does not identify the product or who supplies it.
Check whether it is appropriate for you
Official consumer guidance on food supplements advises following label directions and not exceeding the stated dose. It says supplements should not replace a varied diet, and recommends checking with a healthcare professional if you have a medical condition, use prescribed medicines, are pregnant or are breastfeeding.
A product comparison cannot answer those individual questions. Bring the label or a clear photograph when you ask for advice, so the exact ingredients and strength are available.
Then compare the cost
Use the current price, include delivery where relevant, and compare the number of complete labelled servings in each pack. Our cost-per-serving tool does this calculation. It does not assess quality, effectiveness or suitability.
For a worked comparison of real product information, see our vitamin D label guide. The sources are linked beside the details, so you can follow the comparison back to the manufacturer.
Sources: Consumer food supplements guidance and vitamin D reference guidance. Checked 17 October 2026. General information; not clinically reviewed. Our editorial approach.