The York acupuncture safety study: prospective survey of 34 000 treatments by traditional acupuncturists
MacPherson et al. · BMJ · 2001
Evidence Level
STRONGOBJECTIVE
Assess the safety of acupuncture by documenting types and frequency of adverse events
WHO
574 professional acupuncturists in the United Kingdom
DURATION
4 weeks of data collection
POINTS
Traditional acupuncture — points not specified
🔬 Study Design
Participating acupuncturists
n=574
Prospective documentation of adverse events
📊 Results in numbers
Serious adverse events
Minor adverse events
Mild transient reactions
Aggravation followed by improvement
Percentage highlights
📊 Outcome Comparison
Adverse event rate per 1000 treatments
This large study showed that acupuncture is very safe when practiced by qualified professionals. There were no serious events across more than 34,000 treatments, and minor side effects were rare and temporary.
Article summary
Plain-language narrative summary
The York Safety Study represents a landmark in research on the safety of acupuncture, being one of the largest prospective surveys ever conducted on adverse events in this practice. Carried out in the United Kingdom in 2001, the study involved 574 professional acupuncturists who systematically documented all adverse events over a four-week period, covering 34,407 acupuncture treatments. The primary objective was to establish reliable data on the safety of traditional acupuncture, a crucial issue for the integration of this practice into conventional medicine. The methodology used was rigorous, employing a prospective postal audit system in which practitioners recorded details of any adverse event considered 'significant,' including unusual or dangerous events or events causing significant inconvenience to patients.
Participants represented 31% of all professional acupuncturists registered with the British Acupuncture Council, with a demographic distribution representative of the total practitioner population. The results were exceptionally reassuring regarding the safety of acupuncture. No serious adverse events were reported — defined as those requiring hospitalization, leading to permanent disability, or resulting in death. With 95% confidence, this establishes a maximum rate of serious events of 1.1 per 10,000 treatments.
Forty-three minor adverse events were documented, representing a rate of 1.3 per 1,000 treatments. The most common events included severe nausea and fainting (12 cases), unexpected and prolonged aggravation of existing symptoms (7 cases), and prolonged local pain with bruising (5 cases). Notably, three events were classified as avoidable practitioner errors, including forgotten needles and moxibustion burns. The study also documented mild transient reactions in 15% of treatments, many of which are considered positive signs of therapeutic response.
These included a sensation of relaxation (11.9% of cases), a sensation of energy (6.6%), and mild bruising at the puncture site (1.7%). Particularly interesting was the observation that 966 patients (2.8%) experienced temporary aggravation of existing symptoms, but 86% of these cases were followed by improvement, suggesting the phenomenon known as 'healing crisis.' The clinical implications of this study are significant for patients, practitioners, and health policy makers. The adverse event rate for acupuncture was shown to be comparable to or lower than that of many medications routinely prescribed in primary care, establishing acupuncture as a relatively safe intervention when practiced by qualified professionals. For patients, these data offer reassurance that traditional acupuncture is safe, with minimal risks of serious events.
Limitations of the study include the potential self-reporting bias, in which practitioners may underreport adverse events, and the relatively short four-week observation period. In addition, the study focused only on professionally registered acupuncturists, not covering unregulated practitioners. Representativeness may have been affected by the voluntary participation of only one-third of eligible practitioners. This study established a methodological standard for subsequent research on acupuncture safety and provided essential data that directly influenced clinical guidelines and regulatory policies.
The results contributed significantly to the recognition of acupuncture as a safe practice and to its growing integration into conventional health systems.
Strengths
- 1Largest prospective sample of acupuncture treatments ever studied
- 2Rigorous methodology with prospective audit
- 3Representative practitioner population
- 4Clear definitions of adverse events
Limitations
- 1Potential self-reporting bias by practitioners
- 2Observation period limited to 4 weeks
- 3Only one-third of practitioners participated
- 4Did not include unregulated practitioners
Expert Commentary
Dr. Marcus Yu Bin Pai
MD, PhD · Pain Medicine · Physical Medicine and Rehabilitation · Medical Acupuncture
▸ Clinical Relevance
The safety profile documented in this work has direct impact on clinical decision-making, especially when we evaluate acupuncture as an adjuvant therapeutic option in patients with comorbidities, polypharmacy, or relative contraindications to anti-inflammatories and opioids. Across 34,407 prospectively audited treatments, the absence of serious adverse events — with an upper confidence limit of 1.1 per 10,000 treatments — places acupuncture in a favorable position relative to various pharmacologic interventions in primary care. For the physician managing chronic musculoskeletal pain, fibromyalgia, or headache, these data support the indication with less reticence in vulnerable populations: older adults, pregnant women in the second and third trimesters, patients with NSAID-related gastropathy, and those with renal insufficiency who cannot tolerate conventional analgesics. The minor event rate of 1.3 per 1,000 treatments is concrete information for informed consent, making the pre-procedure conversation more objective and less speculative.
▸ Notable Findings
The finding that deserves attention is the dissociation between transient reactions — present in 15% of treatments — and adverse events proper. Deep relaxation, increased energy sensation, and local ecchymoses are part of an expected physiologic response, not an alarm sign, and the study makes this distinction operational. Equally relevant is the dynamic of transient symptom aggravation: 2.8% of patients reported initial worsening, but 86% of these cases evolved with subsequent improvement. This pattern, which often generates anxiety in the patient and doubt in the attending physician, here receives a solid epidemiologic basis. The three events classified as avoidable errors — forgotten needles and moxibustion burns — reinforce that the documented residual risk is predominantly procedural in nature and, therefore, mitigable through protocol, training, and post-session checklist.
▸ From My Experience
In my practice at the musculoskeletal pain clinic, the safety profile described here is consistent with what I have observed over decades. The transient aggravation followed by improvement is a phenomenon I have learned to verbally anticipate with the patient before the first session — when I do this, the rate of early dropout drops noticeably. I typically see measurable clinical response between the third and fifth session in chronic low back pain and tension cervical pain; patients with myofascial syndrome with active trigger points tend to respond even sooner. For maintenance, the pattern I have observed throughout my career is 8 to 12 initial sessions, with reassessment for progressive spacing. I routinely combine with supervised kinesiotherapy and, when relevant, with dry needling of trigger points in the same session. I do not indicate acupuncture alone in patients with severe decompensated anxiety disorder — the expectation of initial aggravation can precipitate dropout or catastrophizing.
Indexed scientific article
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Scientific Review
Marcus Yu Bin Pai, MD, PhD
CRM-SP: 158074 | RQE: 65523 · 65524 · 655241
PhD in Health Sciences, University of São Paulo. Board-certified in Pain Medicine, Physical Medicine and Rehabilitation, and Medical Acupuncture. Scientific review and curation of every entry in this library.
Learn more about the author →Medical disclaimer: This content is for educational purposes only and does not replace consultation, diagnosis, or treatment by a qualified professional. Some information may be assisted by artificial intelligence and is subject to inaccuracies. Always consult a physician.
Content reviewed by the medical team at CEIMEC — Integrated Centre for Chinese Medicine Studies, a reference in Medical Acupuncture for over 30 years.
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