Can I Take Quercetin with Wegovy? A Clinical Review

What quercetin does to drug handling in people

Quercetin is a plant flavonol found in onions, apples and tea and sold as an over-the-counter dietary supplement. A Drugs@FDA search returns no approved drug application with quercetin as the active ingredient, so it is not an FDA-approved treatment for any condition [7]. In-vitro and rodent work often describes quercetin as a CYP3A inhibitor, but the human studies are small, and the direction of the effect changes with the enzyme being measured.

CYP3A. In a randomized two-period crossover study of 18 healthy men, 500 mg of quercetin daily for 13 days lowered midazolam exposure rather than raising it. Midazolam AUC was 165.5 vs 211.8 ng.h/mL and half-life 2.06 vs 2.75 hours, with the effect seen in men carrying CYP3A5*1 alleles [2]. That is an induction pattern, and it points the opposite way from the in-vitro and animal work [2].

CYP2C9. In an open-label, sequential study of 12 healthy volunteers, 500 mg of quercetin twice daily for 10 days raised diclofenac Cmax, AUC and half-life, lowered apparent oral clearance, and reduced formation of 4-hydroxydiclofenac, the pattern expected from CYP2C9 inhibition [3].

CYP2E1. In 12 healthy subjects given 500 mg twice daily for 10 days, chlorzoxazone Cmax rose 47.8%, AUC rose 69.3%, half-life rose 36.4% and clearance fell 41.6% [5].

CYP1A2 and others. Using caffeine as a probe in 12 volunteers, 500 mg daily for 13 days reduced CYP1A2 activity by 10.4% (95% CI 1.1 to 29.8%), a small change, while CYP2A6 activity rose 25.3%, NAT2 rose 88.7% and xanthine oxidase rose 15.0% [11].

P-glycoprotein and other transporters. The results conflict. Fexofenadine AUC rose 55% (2,005 to 3,099 ng.h/mL) and Cmax rose 68% in 12 subjects taking 500 mg three times daily for 7 days, with oral clearance down 37% [4]. Talinolol went the other way: AUC0-inf was 8,415 ng.h/mL with quercetin vs 10,478 without in 18 subjects after 500 mg daily for 13 days [6]. Saquinavir was unchanged (AUC ratio 0.99, 95% CI 0.65 to 1.50) in 10 adults after 500 mg three times daily for 8 days [8], and cefprozil was unchanged in 24 men given 500 mg daily for 15 days [10].

Does quercetin change semaglutide levels?

Semaglutide is a GLP-1 analogue with 94% sequence homology to human GLP-1 that binds and activates the GLP-1 receptor and delays gastric emptying [1]. It is broken down by proteolytic cleavage of the peptide backbone and beta-oxidation of its fatty acid side chain, not by CYP enzymes, and about 3% of a dose is excreted unchanged in urine [1]. Its elimination half-life is about one week, so semaglutide stays in the body for roughly 5 to 7 weeks after the last 2.4 mg injection or 25 mg tablet [1].

Quercetin exposure is hard to predict even without a second drug. In ileostomy volunteers, absorption was 24% for pure quercetin aglycone, 52% for onion glucosides and 17% for rutinoside, with a plasma half-life of about 25 hours, so repeated intake accumulates [12]. An onion-skin extract produced 4.8 times the AUC and 5.4 times the Cmax of quercetin dihydrate capsules in 12 subjects [13], and between-person variation in plasma levels ran 36% to 57% over two weeks of dosing [14].

Timing with the injection and the tablets

The Wegovy drug interactions section states that semaglutide delays gastric emptying and may affect absorption of oral medicines, and it asks for increased clinical or laboratory monitoring with oral drugs that have a narrow therapeutic index or require clinical monitoring [1]. In pharmacology trials with semaglutide 1 mg injection, semaglutide did not affect the absorption of oral medicines to a clinically relevant degree, and with the semaglutide tablet levothyroxine total exposure rose 33% [1]. No clinically significant effect was seen on lisinopril, warfarin, metformin, digoxin, ethinyl estradiol, levonorgestrel, furosemide or rosuvastatin, and omeprazole did not change semaglutide levels [1].

For Wegovy injection, the label allows dosing at any time of day, with or without meals. Wegovy tablets are labeled for morning use on an empty stomach with up to 4 ounces of plain water, followed by at least 30 minutes before food, drinks, or other oral medicines [1].

Blood glucose with both

Wegovy lowers blood glucose and can cause hypoglycemia. The risk increases with insulin or an insulin secretagogue such as a sulfonylurea, and the label advises considering a lower dose of those when Wegovy is started [1]. In a weight-management trial in adults with type 2 diabetes and BMI 27 or higher, glucose below 54 mg/dL occurred in 6.2% of those on Wegovy 2.4 mg versus 2.5% on placebo [1]. The label says to monitor blood glucose before and during Wegovy treatment in patients with diabetes [1].

Quercetin's effect on glucose is small at best. A meta-analysis of 9 randomized trials in people with metabolic syndrome and related disorders found no overall effect on fasting plasma glucose, HOMA-IR or HbA1c. Lower fasting glucose appeared only in subgroups: trials lasting 8 weeks or more (weighted mean difference -0.94, 95% CI -1.81 to -0.07) and trials using 500 mg/day or more (-1.08, 95% CI -2.08 to -0.07). Insulin fell in subgroups of people under 45 and at doses of 500 mg/day or more [9]. In a separate double-blind crossover of 22 healthy men with high-normal uric acid, 500 mg daily for 4 weeks lowered uric acid by 26.5 micromol/L but did not change fasting glucose or blood pressure [15].

Blood pressure and kidney warnings

Quercetin lowers blood pressure modestly. In a meta-analysis of 7 randomized trials (9 treatment arms, 587 patients), systolic pressure fell 3.04 mmHg (95% CI -5.75 to -0.33) and diastolic 2.63 mmHg (95% CI -3.26 to -2.01). At doses of 500 mg/day or more the drops were 4.45 and 2.98 mmHg, and below 500 mg/day there was no significant effect [16]. The Wegovy label lists hypotension reactions in 1.3% versus 0.4% and syncope in 0.8% versus 0.2% in its trial population [1].

On the kidney side, the Wegovy label warns about acute kidney injury from volume depletion, reported at 0.4 versus 0.2 cases per 100 patient-years (7 versus 4 adults), more often in people with prior renal impairment and during dose titration, often after gastrointestinal fluid loss [1]. A safety review of quercetin cites animal data suggesting it may enhance nephrotoxic effects in an already damaged kidney and lists this among possible critical safety aspects [17].

Stomach and digestive effects

In pooled placebo-controlled trials of Wegovy 2.4 mg (2,116 treated versus 1,261 placebo, up to 68 weeks), nausea occurred in 44% versus 16%, diarrhea 30% versus 16%, vomiting 24% versus 6% and constipation 24% versus 11%. Any gastrointestinal reaction occurred in 73% versus 47%, and 6.8% versus 3.2% stopped treatment because of adverse reactions [1]. The label says Wegovy is not recommended in patients with severe gastroparesis [1].

For quercetin, a review of the supplement safety literature found that adverse effects have rarely been reported in human studies and were mild when they occurred, and that adequate data for long-term use beyond 12 weeks at 1,000 mg/day or more are not available [17]. In a 15-day study of 24 men taking 500 mg daily, no serious adverse events were reported [10].

Doses used in the human studies

The CYP probe studies used 500 mg once daily for 13 days [2][11]. A separate uric-acid study used 500 mg once daily for four weeks [15]. Quercetin 500 mg twice daily was used for 10 days [3][5], and 500 mg three times daily for 7 days with fexofenadine and 8 days with saquinavir [4][8]. Those are the doses that were studied, not recommended doses.

Putting it together

Quercetin is not an FDA-approved drug, and the human evidence behind its main health claims is modest: small reductions in blood pressure and in plasma uric acid are the best-supported effects [7][16][15]. The parts of its human profile that matter for someone taking other medicines are the CYP2C9 and CYP2E1 inhibition and the inconsistent transporter results [3][5][4][6]. On the Wegovy side, the label's practical instructions concern blood glucose monitoring in diabetes and closer monitoring of narrow-therapeutic-index oral drugs [1].