Doubtful knight's spur is highly toxic to humans, cats, and dogs if ingested. Containing methyllycaconitine in its flowers, leaves, and seeds, it can cause severe symptoms. Immediate medical or veterinary attention is critical for poisoning, which causes symptoms including increased heart rate, tremors, and difficulty breathing. Preventing access to doubtful knight's spur and prompt professional care are essential to mitigate adverse effects. Parents must monitor children around doubtful knight's spur.