Supplements · Diets · Metabolic & Cardiometabolic
quercetin decreases fasting glucose
In plain terms: Does quercetin lower blood sugar?
Part of: 🧪 quercetin
Almost all the evidence is from rodents, and even there two of the more rigorous studies found no glucose change. The single human data point used a combination product in 16 people, so it cannot be credited to quercetin.
📅 Last reviewed: 2026-07-26 ⓘ
Evidence ladder
How far up the ladder this claim has climbed. A high consensus on a low rung means "consistent so far," not "proven in people."
Top evidence so far: Human trials (RCT / n-of-1)
How the studies fall
What the evidence shows
Almost entirely preclinical. The only human data point is a 16-person crossover trial of a chrysin-quercetin-rutin COMBINATION product reporting a small fasting-glucose reduction — underpowered, a secondary outcome, and confounded by co-ingredients.
The evidence (10)
| Source | Grade | Stance | Quality | Finding |
|---|---|---|---|---|
| Ibi A, Chang C, Kuo YC, Zhang Y, Do P, Du M, Roh YS, Gahler R, Hardy M, Solnier J 2025 · Antioxidants (Basel, Switzerland) | RCT | supports | moderate | Randomized double-blind crossover PK trial, 16 healthy adults; secondary 30-day daily-use safety arm (n=15) of a micellar chrysin-quercetin-rutin formulation (quercetin dose within formulation not specified). 'Small, but significant, reduct |
| Ali W, Ali M, Sehar M, Shahid S, Shiue YL, Mustafa G, Akhtar B, Sharif A 2026 · Applied biochemistry and biotechnology | animal | supports | low | STZ-nicotinamide-induced diabetic mice; quercetin tested as an individual treatment (dose/duration not specified) alongside Coronopus didymus and Azadirachta indica extracts. 'Individual treatments effectively lowered blood glucose,' though |
| Anuduang A, Laoung-On J, Kraseasintra O, Srichairatanakool S, Rerkasem K, Ounjaijean S, Boonyapranai K 2026 · Biology | animal | supports | low | HFD-induced obese C57BL/6 mice given enzymatic vs non-enzymatic Thai shallot (quercetin-glycoside-rich) extract at 1000-2000 mg/kg/day for 12 weeks after 12-week HFD induction. Both forms 'improved fasting glucose' along with insulin resist |
| Su P, Chen C, Pang L, Wu K, Sun Y 2024 · Reproductive biology and endocrinology : RB&E | animal | supports | moderate | Meta-analysis of 10 animal studies (PCOS rodent models, e.g. letrozole-induced) found quercetin significantly reduced fasting blood glucose (FBG, P=0.01) alongside fasting insulin (P=0.0004) and HOMA-IR (P<0.00001) vs model controls. Exact |
| Chen Z et al 2026 · Research Square | animal | contradicts | moderate | Preprint duplicate of the same STZ-diabetic rat DPN study (12 weeks quercetin): improved pain thresholds and nerve morphology 'without significantly altering blood glucose or body weight' -- explicit null on the glycemic endpoint. |
| Alves ÉR, Silva JGMD, Melo IMF, Santos LCDS, França MMS, Neto CL, Medina VB, Souza FAL, Vieira LD, Teixeira ÁAC, Teixeira VW 2026 · J Biochem Mol Toxicol | animal | supports | low | STZ-diabetic rats, n=10/group, 30 days. Quercetin 40 mg/kg alone: 'the diabetic group continued to have the highest blood glucose levels (569.25 ± 32.57 mg/dL, p < 0.05). The GDQ group had a reduction in blood glucose level (502.50 ± 94.20 mg/dL, p < 0.05).' Authors: 'a moderate reduction in glycemia'. A ~12% decrease that leaves animals severely hyperglycaemic; only insulin (89.50) and melatonin (90.75) normalised. Supports the direction only, weakly: marginal separation given the SD, glucometer reading with fasting state not stated, and a beta-cell-ablation rat model. |
| Alqahtani SA, Alshehri HH, Ashour H, Abdallah H, Rashed L, Badi RM, Mohammed MED, Al-Ani B, Alzamil NM, Albawardi A, Aboulhoda BE 2026 · Metabolites | animal | supports | low | High-fat/high-carb-diet (HFCD) NAFLD rat model, quercetin 50 mg/kg for 4 weeks. HFCD induced hyperglycemia (with dyslipidemia, insulin resistance, liver injury); 'all these parameters were significantly (p<0.01) modulated by quercetin treat |
| Zhang B, Li Y, Fan P, Wang S 2026 · Biological & pharmaceutical bulletin | animal | supports | low | In rats subjected to chronic unpredictable mild stress (a depression model, not a standard T2D/obesity model), quercetin (dose/duration not stated) ameliorated glucose metabolic dysregulation via the bile acid-FXR/TGR5-GLP-1 axis, alongside |
| Chen Z, Li Z, Xue X, Song W, Zhang R, Wang C, Yan B, Sun Q, Wu Q 2026 · Naunyn-Schmiedeberg's archives of pharmacology | animal | contradicts | moderate | STZ-induced diabetic rats treated with quercetin for 12 weeks. Quercetin improved pain thresholds and sciatic nerve morphology (diabetic peripheral neuropathy) but 'without significantly altering blood glucose or body weight' -- a clean, di |
| Onaolapo A et al 2026 · Research Square | animal | supports | low | High-fat/high-sugar diet Wistar rats (n=6/group), quercetin 100 or 200 mg/kg vs metformin 25 mg/kg comparator, duration unspecified. HFHS raised blood glucose among other derangements; 'quercetin improved glucose regulation' along with lipi |
Disagree, or know a study we missed?
We grade by evidence, not opinions. The way to weigh in is to point us to a study we haven't cited (check the evidence table above first), or to flag a problem with one we have. Every submission is reviewed; if it holds up, the grade updates and shows in Science Changes Its Mind.
Opens a short form. You'll sign in with Google so submissions are tied to a real account — we don't display your identity, and we only accept a link we can verify (PubMed, DOI, ClinicalTrials.gov).
Educational only, not medical advice. Grades and scores reflect published evidence weighted by study design and quality; see the methodology.