The numbers on a supplement label follow a few simple rules. Here is what they mean, in plain English, so you can read the builder (and any competitor's product) with confidence.
mg, mcg, g and IU
1 g = 1,000 mg = 1,000,000 mcg. Most ingredients are dosed by weight. A few fat-soluble vitamins are still often shown in IU (International Units), which measure biological activity rather than weight, so every vitamin converts differently:
- Vitamin D: 1 mcg = 40 IU (so 1,000 IU = 25 mcg).
- Vitamin E: 1 IU = 0.67 mg of natural (d-alpha) tocopherol, or 0.45 mg of synthetic (dl-alpha).
- Vitamin A: 1 IU of retinol = 0.3 mcg RAE (retinol activity equivalents), the unit most labels now use.
Sources: NIH ODS vitamin D · vitamin E · vitamin A
CFU: how probiotics are counted
CFU means colony-forming units: the number of live bacteria (or yeast) able to grow. Labels count them in billions, so "10 billion CFU" means ten thousand million live cells per serving.
- Live counts fall over time. Heat, moisture and oxygen slowly kill bacteria. A good label states the count guaranteed at the end of shelf life, not at the time of manufacture.
- The strain matters most. Benefits are linked to specific strains at specific doses, e.g. Lactobacillus rhamnosus GG or L. reuteri DSM 17938. The strain code must be on the label.
- More isn't automatically better. Neither a bigger headline CFU nor a longer list of strains makes a product better on its own. What counts is whether those exact strains were studied at that dose, and how many survive to the end of shelf life. In a multi-strain blend, check that each strain is present at a meaningful level.
Sources: NIH ODS probiotics · ISAPP · ISAPP consumer guide (PDF)
Elemental vs compound weight
Minerals can't be taken on their own; they come bound to another molecule (a citrate, glycinate, oxide and so on). The compound is what goes in the capsule, but your body uses the elemental mineral inside it.
Example: magnesium citrate is about 16% magnesium. So 1,000 mg of magnesium citrate gives roughly 160 mg of elemental magnesium. That's why mineral products are bulky, and why the builder shows both numbers. Upper limits for minerals apply to the elemental amount.
Source: NIH ODS magnesium
Upper limits (UL)
The tolerable upper intake level is the most of a nutrient a healthy adult can take every day, from all sources, without likely harm. It is a safety ceiling, not a target. Children, pregnant women and people on medication may have lower limits.
The builder assumes one serving a day and flags any dose above the adult UL. Where US and EU limits differ, we note the stricter one. Doses near the limit need extra label warnings, so expect your manufacturer to query them.
Sources: EFSA dietary reference values · NIH ODS: what you need to know
% NRV on South African labels
NRV (Nutrient Reference Value) is a standard daily reference amount for a vitamin or mineral. "% NRV" shows how much of that amount one serving gives. For example, if the reference amount for a nutrient is 10 mcg and one serving gives 25 mcg, the label shows 250%.
A high % NRV isn't automatically unsafe (the UL is the safety ceiling), but it must be labelled correctly. Which reference values and label format apply depends on how your product is classified (foodstuff or health supplement/complementary medicine), so your manufacturer's responsible pharmacist or a regulatory consultant should sign off the final label.
Source: SAHPRA complementary medicines
Capsule sizes & fill
- Size 0: about 21.7 mm long, holds roughly 400–600 mg of powder.
- Size 00: about 23.3 mm long, holds roughly 600–800 mg.
- Tablets can carry more per piece (up to about 1,200 mg) but need binders and pressing.
How much fits depends on how fluffy or dense your powder is. Light botanical extracts fill fewer milligrams than dense minerals. If your formula doesn't fit, you need more capsules per serving, a bigger size, a tablet, or a powder. The builder's fill bar shows this as you go.
Excipients: fillers & flow agents
Excipients are the "helper" ingredients that make a product manufacturable. They aren't hidden extras: they must be listed on the label.
- Fillers (e.g. microcrystalline cellulose) bulk out small doses so every capsule fills evenly.
- Lubricants (e.g. magnesium stearate, usually under 1%) stop powder sticking to machines.
- Flow agents (e.g. silicon dioxide) stop clumping so doses stay accurate.
Overage
Some ingredients slowly lose strength on the shelf (vitamin C, some B vitamins, vitamin A and especially probiotics). To make sure the product still contains what the label promises on the expiry date, manufacturers add a little extra at production. This is called overage.
For vitamins it is usually a modest top-up; for probiotics it is often 2 to 5 times the label claim. The builder adds 10% for normal production losses and costs probiotics at 2× (both adjustable). Your manufacturer will set the exact figures from their stability data.
Shelf life & stability
Heat, light, moisture and oxygen are what break supplements down. Shelf life is proven with stability testing: samples are stored in controlled conditions and re-tested over time.
- Light-sensitive ingredients (B12, B2, oils) need opaque or amber packaging.
- Probiotics need moisture-tight packaging (blisters, desiccants) and often cool storage.
- Oils oxidise, so they need antioxidants (like vitamin E) and minimal air in the bottle.
South Africa's heat makes this especially important: ask your manufacturer what storage conditions their shelf life is based on.
