Coronavirus: Can Quercetin Help against COVID-19? (Updated)

What is Quercetin?

Quercetin is a pigment derived from plants in the bioflavonoid category (1). It is found in many common plants and foods that we consume, such as onions, grapes, berries, broccoli, tomatoes, red wine, green tea and apples. In addition, it’s also found in supplements like St. John’s wort, Ginkgo Biloba, American elderberry, and others.

One of the functions of flavonoids such as Quercetin is to act as an antioxidant. Interestingly, Quercetin is the most common flavonoid in the diet as it’s estimated that the average person eats 10–100 mg of it every day (2). Quercetin is also considered a senolytic, meaning it can both get rid of bad cells and help old cells (3).

Update: Quercetin, Vitamin C, Vitamin D and Zinc: Check Out The Evidence

The IBM Modelling Study

A study published by the University of Tennessee and Oak Ridge National Labs used the most powerful IBM supercomputer to model which FDA approved compounds or supplements might interfere with the coronavirus binding to cells (4). To review, the coronavirus uses the ACE 2 (Angiotensin Converting Enzyme) receptor to enter cells. Once in a cell, the coronavirus virus empties its RNA contents and hijacks the cell to start producing more viruses. So preventing the coronavirus from binding to the ACE 2 receptor is a good thing as it means the virus can’t get into your cells. The study modeled various compounds and clocking in at number 5 on the list as those that would be to block the virus was Quercetin.

Dr. Michel Chrétien and Quercetin (Montreal researchers will trial an anti-viral treatment for COVID-19 in China)

The broad spectrum anti-viral medicine known as quercetin has already proven successful at treating Ebola and Zika viruses, says Dr. Michel Chrétien, a researcher at the Clinical Research Institute of Montreal. Now, he and co-researcher Majambu Mbikay are awaiting approval to send the drug to China where a clinical trial will test its effectiveness on COVID-19.

Is There Other Evidence that Quercetin Works Against Coronaviruses?

First, realize that the novel coronavirus is in a family of coronaviruses that includes everything from other SARS viruses that cause serious respiratory problems to the common cold. As a result, Quercetin has been tested against other viruses in this family. For example, a 2004 study showed that it blocked the entry of another SARS coronavirus into cells (5). A 2012 study basically concluded the same thing (6).

Quercetin is not the only strategy, consider other strategies with Immune boosting tips for COVID-19 pandemic.

How About This Coronavirus?

This coronavirus is called SARS-CoV-2 and is different from the others in its family. So has Quercetin been shown to do anything that prevents this novel virus from entering cells? Possibly, a lab study that has yet to be peer-reviewed demonstrated that Quercitin and other compounds showed promise in blocking the SARS-CoV-2 novel coronavirus from entering cells (7).

Are There Clinical Trials?

A Montreal scientist by the name of Michel Chrétien is studying Quercetin (9). He recently received a 1 million dollar donation to begin a clinical trial. That study was proceeding in China, but now that the virus is controlled there, it may have to move back to Montreal.

Quercetin and Zinc

Quercetin acts as a zinc ionophore (PubMed 2014), the same mechanism of action that chloroquine and hydroxychloroquine have via helping zinc pass the cell wall where it might halt viral replication. A zinc ionophore is a compound that facilitate the transport of zinc across the cell membrane. It is known that zinc will slow down the replication of coronavirus through inhibition of enzyme RNA polymerase (PubMed 2010). The COVID-19 is an RNA (RiboNucleicAcid) virus and requires the RNA polymerase to replicate. Do take note that the study publication was a 2010 publication and is referring to a different coronavirus as compared to the latest coronavirus (COVID-19); though both are from the same family of coronaviruses.

The MATH+ Protocol

While high-dose vitamin C is new for COVID-19 treatment, it’s been used as a treatment for sepsis since about 2017. The vitamin C-based sepsis treatment was developed by Dr. Paul Marik, a critical care doctor at Sentara Norfolk General Hospital in East Virginia, which has since adopted it as standard of care for sepsis.

In the interview above, Marik explains how the COVID-19 critical care protocol grew out of his sepsis treatment, as he and other doctors noticed there were many similarities between sepsis and severe COVID-19 infection, in particular the out-of-control inflammatory cascade.

To address the differences between the two conditions, a group of doctors, including Marik, founded the Front Line COVID-19 Critical Care Working Group (FLCCC), and began developing a modified protocol specifically for COVID-19.

The original protocol for COVID-19 is detailed in “COVID-19 Critical Care.” Known as the MATH+ protocol, it involves the use of three key medicines, all of which need to be started within six hours of hospital admission:
  • Intravenous methylprednisolone, to suppress the immune system and prevent organ damage from cytokine storms
  • Intravenous ascorbic acid (vitamin C), to control inflammation and prevent the development of leaky blood vessels in the lungs
  • Subcutaneous heparin (enoxaparin), to thin the blood and prevent blood clots

MATH+ Prophylactic and At-Home Treatment Protocol

The initial MATH+ protocol was released in April 2020. In early July and August, it was updated to include quercetin and a number of optional nutrients and drugs, not only for critical care but also for prophylaxis and mild disease being treated at home.

There is evidence that vitamin C and quercetin co-administration exerts a synergistic antiviral action due to overlapping antiviral and immunomodulatory properties and the capacity of ascorbate to recycle quercetin, increasing its efficacy.

For prophylaxis, the FLCCC recommends:
  • Vitamin C — 500 mg
  • Quercetin — 250 mg to 500 mg
  • Zinc — 75-100 mg/day (acetate, gluconate or picolinate). Zinc lozenges are preferred. After one month, reduce the dose to 30 mg to 50 mg per day
  • Melatonin (slow release) — Begin with 0.3 mg and increase as tolerated to 2 mg at night
  • Vitamin D3 — 1,000 to 4,000 IUs per day
The at-home treatment for mildly symptomatic patients is very similar, but adds several optional drugs, including aspirin (ASA), famotidine (an antacid), ivermectin (a heartworm medication that has been shown to inhibit SARS-CoV-2 replication in vitro). (For dosages, see the Critical Care Management Protocol summary, available on the Easter Virginia Medical School’s site.)

They also recommend monitoring your oxygen saturation with a pulse oximeter and to go to the hospital if you get below 94%. The medical evidence to support each drug and nutrient can be found under “Medical Evidence” on the FLCCC’s website.

Blood Pressure Medications and the Novel Coronavirus

One of the problems recently brought up by experts is that some of the most common blood pressure medications on the market make more of this ACE 2 receptor (called upregulation) (8). What’s a receptor? How does upregulation work?

Your cells have receptors on their surfaces that act as a way for molecules in your blood or plasma to tell the cell what to do or to bring certain molecules into the cell from the outside. These ACE receptors are involved in blood pressure control. The coronavirus hijacks this innocent receptor as a way to get into the cell.

What is upregulation? Your body is very good at working around the effects of drugs. For example, if you try to block that ACE 2 receptor, your body will instruct the cells to make more ACE 2 receptors. This is called upregulation.

More ACE 2 receptors may mean that more viruses can enter cells. Hence, there are concerns that some of the younger people perishing from this disease may be those with metabolic syndrome (overweight, lack of exercise, high triglycerides, and high blood pressure) who have been placed on ACE inhibitors or ARB blood pressure medications.

What are those blood pressure medications? Here’s a complete list:

ACE Inhibitors: benazepril (Lotensin, Lotensin Hct), captopril (Capoten), enalapril (Vasotec), fosinopril (Monopril), lisinopril (Prinivil, Zestril), moexipril (Univasc), perindopril (Aceon), quinapril (Accupril).

ARB (Angiotensin II receptor blockers): azilsartan (Edarbi), candesartan (Atacand), eprosartan (Teveten), irbesartan (Avapro), telmisartan (Micardis), valsartan (Diovan), losartan (Cozaar), and olmesartan (Benicar).

How to Take Quercetin

The usual dose is 500mg to 1,000 mg a day. It’s also sometimes complexed with other supplements such as Bromelain (a digestive enzyme from Pineapples) or Vitamin C. Does it work for sure? No, but the circumstantial evidence might be good enough at this point of time. However, only you can decide, based on what’s presented and without large clinical trials; if the data is compelling enough for you.

Where to Buy Quercetin Online?

You can purchase Quercetin as a dietary supplement online at Lazada Malaysia.


(1) Anand David AV, Arulmoli R, Parasuraman S. Overviews of Biological Importance of Quercetin: A Bioactive Flavonoid. Pharmacogn Rev. 2016;10(20):84–89. doi:10.4103/0973-7847.194044

(2) Bischoff SC. Quercetin: potentials in the prevention and therapy of disease. Curr Opin Clin Nutr Metab Care. 2008 Nov;11(6):733-40. doi: 10.1097/MCO.0b013e32831394b8.

(3) Malavolta M1, Pierpaoli E, Giacconi R, Costarelli L, Piacenza F, Basso A, Cardelli M, Provinciali M. Pleiotropic Effects of Tocotrienols and Quercetin on Cellular Senescence: Introducing the Perspective of Senolytic Effects of Phytochemicals. Curr Drug Targets. 2016;17(4):447-59.

(4) Smith, Micholas; Smith, Jeremy C. (2020): Repurposing Therapeutics for COVID-19: Supercomputer-Based Docking to the SARS-CoV-2 Viral Spike Protein and Viral Spike Protein-Human ACE2 Interface. ChemRxiv. Preprint.

(5) Yi L, et al. Small Molecules Blocking the Entry of Severe Acute Respiratory Syndrome Coronavirus into Host Cells. Journal of Virology Sep 2004, 78 (20) 11334-11339; DOI: 10.1128/JVI.78.20.11334-11339.2004

(6) Nguyen TTH, Woo HJ, Kang HK, Nguyen VD, Kim YM, Kim DW. et al. Flavonoid-mediated inhibition of SARS coronavirus 3C-like protease expressed in Pichia pastoris. Biotechnol Lett. 2012;34:831-8

(7) Khaerunnisa S, et al. Potential Inhibitor of COVID-19 Main Protease (Mpro) from Several Medicinal Plant Compounds by Molecular Docking Study. Preprints (

(8) Fang L, Karakiulakis G, Roth M. Are patients with hypertension and diabetes mellitus at increased risk for COVID-19 infection? Lancet Respir Med. 2020 Mar 11. pii: S2213-2600(20)30116-8. doi: 10.1016/S2213-2600(20)30116-8.

(9) MacClean’s. A made-in-Canada solution to the coronavirus outbreak? Accessed 3/19/20.


Read more: Coronavirus

COVID-19 is an emerging, rapidly evolving situation.
Get the latest public health information from CDC:
Get the latest research from NIH:

Related: Can Vitamin C Protect You Against COVID-19?


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