I receive many calls per week where people enquire where they can purchase quercetin. I think this is in part due to the YouTube channel “MedCram” where a Dr. Seheult highlights quercetin as a valid treatment for COVID. In this blog I will be explaining what quercetin is, and the most effective way to consume it, to get maximise results.

What is quercetin?

Plants have an immune function, that protects them from environmental stressors. This immune function is performed by flavonoids, one flavonoid is quercetin-glycoside. Flavonoids are the white or yellow pigment in plants (Pengelly, 2004). When consumed by humans, these flavonoids act as antioxidants (Bone & Mills, 2013).

What is the link to COVID?


Recent studies have indicated that quercetin blocks the inflammatory pathway, that causes the most damage in those infected by COVID (Saeedi-Boroujeni et al., 2021). So, it would stand to reason people are looking to purchase this magical flavonoid.

Back in 2013 while scientists were exploring the antioxidant activity of quercetin. The scientists compared the use of a supplement vs whole food administration of the constituent. It was found that when the isolated constituent was consumed, there were no traces of the constituent in the blood samples of the individual. When the constituent was consumed as part of a whole plant, there was a maximum blood level of quercetin detected within 5 hours (Bone & Mills, 2013). This is an interesting observation when considering the most effective dose, and form to take the constituent in.

Prescribing quercetin.

The optimal dosage of quercetin is 200-1500mg per day in a divided dose during the day (Braun & Cohen, 2014). This dosage is made considering consumption of quercetin in an isolated form, and not as part of a whole.

What does beg mentioning at this point, is that the content of quercetin in the herb, does not limit the anti inflammatory power of the plant. Remember that each herb has 100’s of constituents, that work together, to perform the function. This particular study isolated the quercetin content and looked at just that particular constituent, and its health benefits. Another study, that would be more accurate is to look at the anti inflammatory action of each herb, in clinical trials, regardless of quercetin content.


Bone, K., & Mills, S. (2013). Principles and Practice of Phytotherapy: Modern Herbal Medicine (2nd ed.). Churchill Livingstone.

Braun, L., & Cohen, M. (2014). Herbs & Natural Supplements. Elsevier Gezondheidszorg.

Dabeek, W. M., & Marra, M. V. (2019). Dietary Quercetin and Kaempferol: Bioavailability and Potential Cardiovascular-Related Bioactivity in Humans. Nutrients, 11(10), 2288. https://doi.org/10.3390/nu11102288

Gao, S., Jiang, W., Yin, T., & Hu, M. (2010). Highly Variable Contents of Phenolics in St. John’s Wort Products Affect Their Transport in the Human Intestinal Caco-2 Cell Model: Pharmaceutical and Biopharmaceutical Rationale for Product Standardization. Journal of Agricultural and Food Chemistry, 58(11), 6650–6659. https://doi.org/10.1021/jf904459u

Keser, S., Celik, S., Turkoglu, S., Yilmaz, O., & Turkoglu, I. (2014). The investigation of some bioactive compounds and antioxidant properties of hawthorn (Crataegus monogyna subsp. monogyna Jacq). Journal of Intercultural Ethnopharmacology, 3(2), 51–55. https://doi.org/10.5455/jice.20140120103320

Laila, O., Murtaza, I., Abdin, M. Z., Ahmad, S., Ganai, N. A., & Jehangir, M. (2014). Development and validation of HPTLC method for simultaneous estimation of diosgenin and quercetin in fenugreek seeds (Trigonella foenum-graceum). International Scholarly Research Notices.

Pengelly, A. (2004). The Constituents of Medicinal Plants: An introduction to the chemistry and therapeutics of herbal medicine (2nd ed.). Routledge.

Saeedi-Boroujeni, A., Mahmoudian-Sani, & Mohammad-Reza. (2021). Anti-inflammatory potential of Quercetin in COVID-19 treatment. Journal of Inflammation, 18(1), 3. https://doi.org/10.1186/s12950-021-00268-6

Zhang, Z., Chen, S., Mei, H., Xuan, J., Guo, X., Couch, L., Dobrovolsky, V. N., Guo, L., & Mei, N. (2015). Ginkgo biloba leaf extract induces DNA damage by inhibiting topoisomerase II activity in human hepatic cells. Scientific Reports, 5(1). https://doi.org/10.1038/srep14633

Leave a Reply