Red yeast rice
Herbal products and dietary supplements
Herbal products and dietary supplementsPregnancy: contraindicated
There are no safety studies, so it is not recommended in pregnancy or breastfeeding.
Rice fermented with Monascus mould. Some products contain monacolin K, identical to lovastatin, so they act, and harm, like a statin.
Also called: Monascus purpureus fermented rice, Monacolin K (= lovastatin)
Quick facts
- Group
- Herbal products and dietary supplements
- Target
- HMG-CoA reductase (via monacolin K)
- Used for
- Promoted for high cholesterol
- Key effects
- Muscle pain · Digestive problems
- Monitor
- Lipid profile · Muscle symptoms
No doses: the clinician sets them by the current guideline.
Mechanism of action
The figure shows simvastatin, a close semi-synthetic relative of lovastatin (monacolin K), in the active site of human HMG-CoA reductase.
Depending on the fungal strain and fermentation, the rice contains monacolins. Monacolin K has the same structure as lovastatin: it inhibits HMG-CoA reductase, the rate-limiting step of cholesterol synthesis, so the liver makes less cholesterol and takes up more LDL. Products high in monacolin K lower cholesterol; their content varies enormously, and some contain the kidney toxin citrinin.
- Monacolin K (= lovastatin) is absorbed from the product
- It inhibits HMG-CoA reductase in the liver
- Less cholesterol synthesis, more LDL receptors
- LDL falls; statin-type muscle and liver risks
Indications
- Promoted for high cholesterol: high-monacolin products may lower it; low-monacolin products may not work Atherosclerosis and dyslipidaemia →
Adverse effects
Common
- Muscle pain
- Digestive problems
- Raised liver enzymes
Contraindications
- Use together with a prescribed statin
- Pregnancy and breastfeeding
- Liver disease or previous statin muscle injury
Key interactions
- Prescribed statins
- Duplicate therapy and higher risk of muscle injury
- Medicines that interact with statins (for example strong CYP3A4 inhibitors such as clarithromycin)
- Higher monacolin K levels and myopathy risk, as with lovastatin
What is monitored
- Lipid profile
- Muscle symptoms and creatine kinase if they appear
- Liver and kidney function
Pregnancy and breastfeeding
There are no safety studies, so it is not recommended in pregnancy or breastfeeding.
Nursing care
- Ask every patient about herbal products and supplements and record them with the medicine list
- Check that patients are not taking red yeast rice together with a prescribed statin
- Teach to report unexplained muscle pain or dark urine
- Teach that «natural» does not mean safe and that supplements are not approved as medicines before sale
Pharmacokinetics
- Absorption
- Taken by mouth; the amount of monacolin K is rarely on the label and varies widely between brands
Test yourself
Think of the answer, then tap the question to see it.
Which statin is identical to monacolin K?
Lovastatin.
Why do red yeast rice products differ so much in effect?
Monacolin K content varies widely between brands and is rarely stated on the label.
Which contaminant of red yeast rice can damage the kidneys?
Citrinin.
Connections
← Back to the class: Herbal products and dietary supplements
Educational content on how drugs work; not a prescribing guide and no substitute for a health professional's advice. No doses are given.
Sources: Red Yeast Rice: What You Need To Know (National Center for Complementary and Integrative Health (NCCIH), 2022); DailyMed - LOVASTATIN tablet (DailyMed (U.S. National Library of Medicine), 2026).
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Representative model, for educational purposes only.