Red yeast rice is rice fermented with the mould Monascus purpureus. It has been a food in China for around two thousand years, and it is sold in American pharmacies as a cholesterol supplement, on the shelf, without a prescription.
The reason it lowers cholesterol is not mysterious and not herbal. The mould produces monacolin K, and monacolin K is lovastatin — not similar to it, not related to it. The same molecule. Lovastatin was approved by the FDA in 1987 as one of the first statins, and it is still prescribed today.
It is the same molecule as lovastatin
Which means the dose is whatever the bottle happens to contain
A prescription for lovastatin states a number — 10 mg, 20 mg, 40 mg — and a factory inspected by the FDA has to put that number in the tablet. Red yeast rice is a supplement, so nobody has to.
When researchers have bought commercial red yeast rice products and measured what was in them, the monacolin K content has varied enormously between brands — in published analyses by around a hundred-fold, with some products containing almost none at all. Two bottles on the same shelf, both labelled the same way, can be a meaningful statin dose and a placebo.
The risks come with it, but the monitoring does not
Statins carry real and well-characterised risks: muscle pain, rarely serious muscle breakdown, and effects on the liver. Those risks belong to the molecule, so red yeast rice carries them too. What it does not carry is the rest of the prescription — the prescriber who checks what else you take, the liver testing, the pharmacist who notices that you are also on a drug that raises statin levels dangerously.
The FDA has also repeatedly found red yeast rice products containing lovastatin at drug-like levels and taken enforcement action, on the basis that a supplement containing an approved drug is an unapproved drug rather than a food.
And it is frequently the more expensive option
This is the part that matters most on this site. Lovastatin is a generic that has been off patent for decades and is among the cheapest drugs in American pharmacies. A month of branded red yeast rice capsules often costs more than a month of the drug it is standing in for — so the substitution can cost more money for an unknown dose of the same compound.
Price lovastatin here before deciding. If the number surprises you, that is the point of this site.