The short answer
Willow bark has not been shown to increase quinine-related bleeding or low platelet counts. Quinine can independently cause serious immune thrombocytopenia, while willow’s limited platelet-function evidence does not establish that combined risk.
What this answer covers
Willow bark extracts with varying species and salicin content; not aspirin or purified acetylsalicylic acid.
- Supplement or preparation
- Willow Bark
- Medication ingredient
- quinine
Quinine’s platelet warning is serious
Quinine can cause immune-mediated thrombocytopenia and other serious blood disorders. This established medicine risk is not evidence that willow bark increases it.
The willow trial measured a different endpoint
A small study found weaker effects on some platelet-aggregation measures than aspirin, and no group difference with collagen stimulation. It did not measure a quinine interaction, clinical bleeding or a fall in platelet count.
Do not equate willow with aspirin
Salicin-containing willow preparations differ from acetylsalicylic acid. A platelet-function surrogate cannot establish immune platelet destruction or an aspirin-equivalent bleeding effect.
Review symptoms promptly
Tell the clinician about willow and other pain products. New unusual bruising or bleeding during quinine treatment warrants prompt medical assessment. No proven protective spacing interval or safe combined dose was established.
Evidence and practical considerations
Side effects & toxicity
No exact quinine-willow bleeding or thrombocytopenia evidence. Willow platelet aggregation surrogate is not immune platelet-count loss; weaker-than-aspirin effect and collagen null retained. Intrinsic quinine immune toxicity does not validate additive claim.
- Exact scope
- Willow bark extracts with varying species and salicin content; not aspirin or purified acetylsalicylic acid. with Quinine sulfate oral capsules, not quinidine or homeopathic products.
- Medication form and route
- oral medication; oral supplement
What remains uncertain
- No unmeasured pair incidence, blanket class transfer or arbitrary spacing interval.
Factors that may matter: Preparation; Dose; Other medicines; Organ function.
Read the supporting source summaries
Source 1: current product label
dailymed.nlm.nih.gov · Source check Sep 11, 2026
Population: People prescribed quinine
Aluminum/magnesium antacids may delay/decrease absorption; avoid coadministration. Sodium bicarbonate may increase plasma quinine through urinary alkalinization. Immune thrombocytopenia is a separate serious risk.
How this applies: Exact quinine RxCUI 9071 IN, with stated salt/formulation/route bridge.
Exact route and formulation apply. Label precautions do not quantify untested botanical pairs or support arbitrary supplement doses.
Source 2: Original human study
pubmed.ncbi.nlm.nih.gov · Source check Sep 11, 2026
Population: 51 participants across randomized back-pain and separate ischemic-heart-disease groups.
Some platelet aggregation responses were modestly reduced versus placebo; effect far smaller than aspirin, with no group difference using collagen.
How this applies: Surrogate platelet function, not bleeding or platelet-count change; no quinine co-use. Willow extract is not aspirin.
Surrogate platelet function, not bleeding or platelet-count change; no quinine co-use. Willow extract is not aspirin.
Research assessment: · Open full citations ↗
Review and change history
- Publication status
- Published research summary
- Clinical review
- Not yet recorded
| Date | Update |
|---|---|
| Research summary published | |
| Editorial update | |
| Corrected missing spaces between numbers and units or words in the copy before registration; evidence and conclusions unchanged. | |
| Article prepared | |
| Prepared exact quinine article with formulation-specific evidence and uncertainty. |
Article revision: 5a258f4bdadb995b
This guide brings together the evidence records used by our interaction checker. Each finding retains its own preparation limits, research date, and source summaries.
Full citations require verification. Reading this answer and the source summaries does not.
Taking other supplements or medications?
Use the checker to explore your other combinations. Ask a pharmacist to review the exact products, amounts and medical conditions in your complete list.
Open the interaction checkerInformation, not medical advice. Do not change prescribed treatment based on this guide.