Quercetin and Zinc: FLCCC Protocol for Prevention of COVID-19

FLCCC - The Front Line COVID-19 Critical Care (FLCCC) Alliance was initially formed as a working group under “emergency” conditions of the early COVID-19 pandemic in response to multiple early reports of COVID patients with an inexplicably high need for prolonged mechanical ventilation and an excessive mortality associated with the prevailing “supportive care only” recommendations disseminated by the majority of national and international health care organizations.



As a group of highly published leaders in critical care with expertise in therapies directed at severe infections, in particular “HAT” therapy first developed by Dr. Paul Marik for the treatment of bacterial sepsis, and along with published high patient survival rates from our centers, we were contacted by equally concerned and motivated colleagues from other specialties.

With the increasing publications in addition to our rapidly accumulating personal clinical experiences and investigations into the pathophysiology of COVID-19 patients, we formulated the MATH+ Hospital Treatment Protocol in March 2020. On August 5, 2020, we published our findings in the rationale paper Scientific Review of COVID-19 and MATH+.

In October 2020, the FLCCC Alliance identified, based on a review of the recent and rapidly emerging clinical trials evidence, that ivermectin, an anti-parasitic medicine, has highly potent real-world, anti-viral, and anti-inflammatory properties against SARS-CoV-2 and COVID-19. This conclusion is based not only from multiple in-vitro and animal models, but from numerous clinical trials from centers and countries around the world showing repeated, consistent, large magnitude improvements in clinical outcomes when ivermectin is used not only as a prophylactic agent but also in mild, moderate, and even severe disease states. Further, data from large “natural experiments” that appear to have occurred when various regional health ministries and govern­mental authorities within South American countries initiated “ivermectin distribution” campaigns which then led to temporally associated decreases in case counts and case fatality rates.

Based on these findings, the FLCCC team has developed the I-MASK+ protocol for prophylaxis and at home treatment of early stage disease. You can read the FLCCC Scientific Review of the Emerging Evidence Supporting the Use of Ivermectin in the Prophylaxis and Treatment of COVID-19.

A more detailed story of the inception and evolution of the FLCCC Alliance can be read here.


Quercetin and Vitamin C

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 prevention, the Front Line COVID-19 Critical Care Working Group, FLCCC recommends (updated December 17th, 2020):
  • Vitamin D3 — 1000–3000 IU/day. Note RDA (Recommended Daily Allowance) is 800–1000 IU/day. The safe upper-dose daily limit is likely < 4000 IU/day. [1-22] Vitamin D insufficiency has been associated with an increased risk of acquiring COVID-19 and from dying from the disease. Vitamin D supplementation may therefore prove to be an effective and cheap intervention to lessen the impact of this disease, particularly in vulnerable populations, i.e. the elderly, those of color and obese.
  • Vitamin C - 500 mg BID (twice daily) and Quercetin 250 mg daily. It is likely that vitamin C and quercetin have synergistic prophylactic benefit. Quercetin should be used with caution in patients with hypothyroidism and TSH levels should be monitored.  
  • Melatonin (slow release): Begin with 0.3 mg and increase as tolerated to 2 mg at night. 
  • Zinc: 30–50 mg/day (elemental zinc). Zinc lozenges are preferred.
  • B complex vitamins
  • Ivermectin for prophylaxis in high-risk individuals (> 60 years with co-morbidities, morbid obesity, long term care facilities, etc). 0.15–0.2 mg/kg Day 1, Day 3 and then weekly for 10 weeks, followed by biweekly dosing. (also see ClinTrials.gov NCT04425850). NB. Ivermectin has a number of potentially serious drug-drug interactions. Please check for potential drug interaction at Ivermectin Drug Interactions - Drugs.com. The most important drug interactions occur with cyclosporin, tacrolimus, anti-retroviral drugs, and certain anti-fungal drugs. 
COVID19 FLCCC Ivermectin Quercetin Zinc Vitamin B C D Melatonin
Image credit: Covid19criticalcare.com

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.

June 19, 2020, Marik published the paper “Quercetin and Vitamin C: An Experimental, Synergistic Therapy for the Prevention and Treatment of SARS-CoV-2 Related Disease (COVID-19)” in the journal Frontiers in Immunology, which notes:

“Ascorbic acid is a crucial vitamin necessary for the correct functioning of the immune system. It plays a role in stress response and has shown promising results when administered to the critically ill. Quercetin is a well-known flavonoid whose antiviral properties have been investigated in numerous studies.

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.

Safe, cheap interventions which have a sound biological rationale should be prioritized for experimental use in the current context of a global health pandemic.”


The paper presents evidence for the use of vitamin C and quercetin — based on their biological actions and pharmacokinetics profiles — both as prophylaxis in high-risk populations, and as an adjunct to drugs such as Remdesivir or convalescent plasma in the treatment of hospitalized COVID-19 patients.


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