By SupplementenscannerHow we compare
The upper figures the NHS sets, and the figures on the front of a pack
The NHS puts an upper figure beside three of these: do not take more than 100 micrograms (4,000 IU) of vitamin D a day, do not take more than 25mg of zinc supplements a day unless advised to by a doctor, and 350μg or less a day of selenium is unlikely to cause any harm.
A British pack prints its own figures: 1,000mg is the usual vitamin C tablet, 15mg or 25mg the usual zinc one, and 55μg, 100μg or 200μg the usual selenium. Where a pack figure and an NHS figure happen to match, they are still answering different questions, and a price per capsule answers neither. That is why the label figure is read first.
Micrograms on one box, international units on the next
Vitamin D3 is the one ingredient here sold in two units at once: 10 micrograms is 400 IU and 25 micrograms is 1,000 IU, and both spellings sit in the same category. Cholecalciferol is D3 and ergocalciferol is D2; a vegan pack takes its D3 from lichen rather than from wool grease. Drops are sold in millilitres and only earn a per-unit price when the pack states a number of drops or servings. The same capsules turn up on joints and bones and menopause.
Zinc: what the compound weighs and what the mineral weighs
Zinc prints its compound on the front and its elemental content a line below, in milligrams, and only that second figure makes two tablets comparable. Gluconate, citrate, picolinate, bisglycinate and oxide carry different elemental weights at the same tablet weight, and lozenges are a format of their own. The same arithmetic is worked through for another mineral in buying magnesium.
Selenium is dosed in micrograms per tablet, as selenomethionine, sodium selenite or selenium-enriched yeast, and the form decides what the microgram figure is attached to.
Vitamin C, quercetin and the %NRV column
Vitamin C is where the front of a pack hides the most. Ascorbic acid, buffered vitamin C as calcium ascorbate, Ester-C as a trade name for that buffered form and time-release tablets can all print the same 1,000mg. Effervescent tablets and powders state a dose per tablet or per scoop, and without a count on the pack only the tub price is left.
Quercetin is in milligrams per capsule, often as quercetin dihydrate, and is frequently sold with vitamin C, zinc or bromelain beside it; where the label adds those into a single total, only the quercetin line compares. A multivitamin gathers the vitamins and minerals from this list into one tablet at a lower dose than any single tub, and one tablet a day or two changes the daily cost while the ranking stays per tablet.
Echinacea by the box, probiotics by the capsule
Echinacea has no category of its own and is found by name, so the pack keeps its whole price. That is the fairer measure here, because the word covers four objects that no single unit converts between. A tincture is sold by the millilitre and states an alcohol percentage. A capsule states milligrams of dried herb. An extract states a ratio, 4:1 for instance. A tea states neither. Purpurea, angustifolia and pallida are three plants besides, and root is not the aerial part. Divide the box price by the number of doses the pack states.
Probiotics are compared per capsule on two label facts: the strains written out in full (Lactobacillus, Lacticaseibacillus, Bifidobacterium) and the CFU per capsule, counted at manufacture or at end of shelf life depending on the brand. The same capsules appear on digestion and fibre. For omega-3 the 1,000mg of fish oil on the front is not the measure: EPA and DHA two lines down are, and algae oil leads on DHA. Buying fish oil works through that line.
Boots and Holland & Barrett turn up in the related searches as places rather than products, and neither is scanned here. What the remaining words on a pack settle is set out in reading a supplement label.