Fiber

Which medicines interact with fiber?

Updated 4 Nov 2026

Short answer

Psyllium can delay the absorption of other medicines, so it is taken apart from them. The European Medicines Agency (EMA) names:[1]

  • minerals and vitamin B12[1]
  • cardiac glycosides, such as digoxin[1]
  • coumarin blood thinners[1]
  • carbamazepine, a seizure medicine, and lithium[1]

The time gap differs by source. The EMA says 30 to 60 minutes, MedlinePlus says 3 hours for digoxin, aspirin and nitrofurantoin, and Health Canada says a few hours.[1][2][3]

Other medicines need care for other reasons. Doses of diabetes medicine and thyroid hormone may need to change, and opioids slow the gut, which raises the risk of a blockage.[1] Anyone who takes a medicine every day should ask a doctor or pharmacist before starting psyllium.[2]

Sources (3)

  1. Community herbal monograph on Plantago ovata Forssk., seminis tegumentum. European Medicines Agency, HMPC, 2013. www.ema.europa.eu
  2. Psyllium: MedlinePlus Drug Information. MedlinePlus, US National Library of Medicine, 2024. medlineplus.gov
  3. Natural Health Product Monograph: Psyllium, Plantago ovata. Health Canada, 2018. webprod.hc-sc.gc.ca

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