Written by Helen Cooke, Helen Seers and the CAM-Cancer Consortium.
Updated January 29, 2015


Is it safe ?

Adverse events

Cyanide is believed to be the active cancer-killing ingredient in Laetrile, which has caused concern over toxicity. Adverse events linked with Laetrile treatment are like the symptoms of cyanide poisoning. These symptoms include: nausea and vomiting, headache, dizziness, bluish discolouration of the skin due to lack of oxygen in the blood, liver damage, abnormally low blood pressure, difficulty walking, droopy eyelids, fever and mental confusion, coma and death. Several deaths have been attributed to Laetrile17,18. If taking Laetrile orally, the potential risk of cyanide poisoning symptoms are increased if any from the list of foods containing Laetrile are eaten (see above) or high doses of vitamin C are taken19. A recent adverse drug reaction case of severe life-threatening accidental cyanide poisoning has been reported in Australia. The report suggests a patient increased her risk of cyanide toxicity by co-ingesting amygdalin with a megadose of Vitamin C (4800mg)20. More severe adverse events (i.e. cyanide poisoning) are seen when Laetrile is administered orally than when it is given by injection, as intestinal bacteria contain enzymes that promote the release of cyanide in the digestive system21.

A review concluded that the risk of people developing cyanide poisoning who ingest Laetrile is high6.


In addition to the above serious concerns, for those with liver problems/damage Laetrile may compromise liver function18. Furthermore, this treatment should be avoided by pregnant or breast-feeding women.


Ascorbic acid (vitamin C) may increase the toxicity of Laetrile/Amygdalin/B1719.


Helen Cooke, Helen Seers, CAM-Cancer Consortium. Laetrile [online document]. http://www.cam-cancer.org/CAM-Summaries/Dietary-approaches/Laetrile. January 29, 2015.

Document history

Assessed as up to date in January 2015 by Barbara Wider.
Updated in April 2014 by Barbara Wider.
Assessed as up to date in December 2012 by Helen Cooke.
Most recent update and revision in December 2011 by Helen Cooke.
Fully revised and updated in July 2009 by Helen Cooke.
Summary first published in September 2005, authored by Helen Seers.


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