Fiber

Does fiber lower blood sugar?

Updated 4 Nov 2026

Short answer

In people with diabetes, yes, by a modest amount. In 29 trials with 1,517 adults with type 2 diabetes, soluble fiber supplements lowered HbA1c, a blood test of average blood sugar, by 0.63% and fasting glucose by 0.89 mmol/L.[1] A review of more fiber in diabetes found HbA1c 2.00 mmol/mol lower in 33 trials. These results varied widely between trials.[1][2]

In healthy adults, fewer than 20% of interventions with isolated fibers lowered blood glucose.[3]

The European Medicines Agency says people with diabetes should use psyllium only under medical supervision, because their diabetes medicine may need to change.[4] Health Canada says not to use it when blood sugar is hard to control.[5]

Sources (5)

  1. Effects of soluble fiber supplementation on glycemic control in adults with type 2 diabetes mellitus: A systematic review and meta-analysis of randomized controlled trials. Xie Y, Gou L, Peng M, Zheng J, Chen L Clin Nutr, 2021. PMID 33162192
  2. Dietary fibre and whole grains in diabetes management: Systematic review and meta-analyses. Reynolds AN, Akerman AP, Mann J PLoS Med, 2020. PMID 32142510
  3. The Effect of Isolated and Synthetic Dietary Fibers on Markers of Metabolic Diseases in Human Intervention Studies: A Systematic Review. Armet AM, Deehan EC, Thöne JV, Hewko SJ, Walter J Adv Nutr, 2020. PMID 31342059
  4. Community herbal monograph on Plantago ovata Forssk., seminis tegumentum. European Medicines Agency, HMPC, 2013. www.ema.europa.eu
  5. Natural Health Product Monograph: Psyllium, Plantago ovata. Health Canada, 2018. webprod.hc-sc.gc.ca

More about fiber

What is fiber?How does fiber lower cholesterol?How much fiber do you need per day?What is fiber used for?How long does fiber take to lower cholesterol?Is fiber safe?

For education; not medical advice. Talk to a doctor before you start, stop or change a supplement.