There's an old joke about homeopathy, which goes something like this: A man overdosed on homeopathic medicine. He forgot to take his pills.

Homeopaths believe (mistakenly) that substances that cause specific symptoms in healthy people can be used to treat those symptoms in unhealthy patients. According to homeopathists, the more the substance is diluted, the stronger it is, and the better it is at treating patients. Hence why the hypothetical man who forgot to take his pill died in the above joke – he received a stronger homeopathic dose because he had absolutely none of the active ingredient. 

While scientifically bunkum, this idea of dilution at least does one thing for the health of patients of homeopathists; it protects them from potentially deadly ingredients in their alternative medicine. Normally, homeopathists dilute the active ingredient down to such a minuscule amount that there is just the tiniest trace of the ingredient left. This won't do anything for you, other than perhaps a mild placebo effect, but at least you can be pretty confident that you aren't being poisoned. You're basically eating very expensive sugar, or drinking slightly funny-tasting water.

Unfortunately, sometimes the vital dilution part is not done properly, resulting in a weaker dose from the homeopath's perspective – and occasionally overdoses of deadly ingredients from a real medical perspective. 

In 2021, one such overdose occurred when a 53-year-old male patient showed up at the emergency department with symptoms including confusion, drowsiness, dizziness, feelings of anxiety, muscle weakness, dry mouth, difficulty speaking, and visual impairment. These symptoms came on shortly after he took 30 drops of a homeopathic remedy containing Atropa belladonna, aka deadly nightshade, a plant that was used to make poison arrows by Ancient Romans.

Investigating the cause of his symptoms, his doctors discovered that the manufacturer had inadvertently placed a whole lot more belladonna than they should have.

"We were able to determine the atropine concentration in the homeopathic mixture as approximately 3 mg/mL instead of the declared 0.005 mg/mL which resulted in a 600-fold overdose," the doctors write in their report.

Fortunately, the patient recovered over the next 12 hours without medical intervention. 

"We would like to remind clinical physicians to also enquire about alternative medications and be vigilant for the onset of symptoms related to homeopathic or holistic preparations," the team concluded in their case report. "When prescribing homeopathic remedies, it is preferable to use original preparations from established drug manufacturers."

The case report is published in the journal Clinical Toxicology.