Boron
A trace mineral with no official UK target, but a real upper limit once you go looking.
Boron is a trace mineral involved in bone mineralisation and steroid hormone metabolism, though the UK has not set a formal reference intake for it the way it has for calcium or iron. The US NIH does define a tolerable upper limit of 20mg a day. Boron glycinate absorbs well and is a common supplement form; calcium fructoborate is a naturally-derived organic compound also used in bone and joint formulas. Borax (sodium tetraborate), the older industrial-adjacent form, is absorbed less efficiently and is less commonly used in modern supplements.
Reference values
Daily reference values from official nutrition authorities. These are population reference figures, not personal recommendations.
| RDA | Upper limit | Source |
|---|---|---|
| 3 mg | 20 mg | UK |
Forms and bioavailability
Not all forms are absorbed equally. The form on your supplement label affects how much your body can actually use.
| Form | Absorption | With food | Timing | Evidence |
|---|---|---|---|---|
| boron glycinate | Higher | Either | Either | Likely |
| calcium fructoborate | Typical | With food | Either | Likely |
| borax (sodium tetraborate) | Lower | Either | Either | Possible |
Stack Almanac totals your boron intake across every supplement you log and checks it against the 20mg upper limit, even though no single UK target exists to compare it to.
Track your Boron in Stack Almanac
Last reviewed: 2026-07-08. Reference values are adult-general RDAs from UK. Individual needs may vary. This page is for informational purposes only and is not a substitute for professional medical advice.