After its heyday in the Tang dynasty Daoist alchemy continued to flourish during the Song dynasty (960–1279) period. However, since six Tang emperors and many court officials died from elixir poisoning, Song alchemists exercised more caution, not only in the composition of the elixirs themselves, but also in attempts to find pharmaceutical methods of counteracting the toxic effects. The number of ingredients used in elixir formulas was reduced and there was a tendency to return to the ancient and difficult terminology of the Cantongqi, perhaps to conceal the processes from rash and ignorant operators. Psycho-physiological neidan alchemy became steadily more popular than laboratory waidan alchemy.
During the Song dynasty, the practice of consuming metallic elixirs was not confined to the imperial court and expanded to anyone wealthy enough to pay. The author and official Ye Mengde (1077–1148) described how two of his friends had died from elixirs of immortality in one decade. First, Lin Yanzhen, who boasted about his health and muscular strength, took an elixir for three years, "Whereupon ulcers developed in his chest, first near the hairs as large as rice-grains, then after a couple of days his neck swelled up so that chin and chest seemed continuous." Lin died after ten months of suffering, and his doctors discovered cinnabar powder had accumulated in his pus and blood. Second, whenever Xie Renbo "heard of anyone who had some cinnabar subdued by fire he went after it, caring nothing about the distance, and his only fear was that he would not have enough." He also developed ulcers on the chest. Although his friends noticed changes in his appearance and behavior, Xie did not recognize that he had been poisoned, "till suddenly it came upon him like a storm of wind and rain, and he died in a single night".
The scientist and statesman Shen Kuos 1088 Dream Pool Essays' suggested that mercury compounds might be medicinally valuable and needed further study—foreshadowing the use of metallic compounds in modern medicine, such as mercury in salvarsan for syphilis or antimony for visceral leishmaniasis. Shen says his cousin once transformed cinnabar into an elixir, but one of his students mistakenly ate a leftover piece, became delirious, and died the next day.
Su Shi (1037–1101), the Song dynasty scholar and pharmacologist, was familiar with the life-prolonging claims of alchemists, but wrote in a letter that, "I have recently received some cinnabar (elixir) which shows a most remarkable colour, but I cannot summon up enough courage to try it".
The forensic medical expert Song Ci was familiar with the effects of metal poisoning, and his c. 1235 Collected Cases of Injustice Rectified handbook for coroners gives a test for mercury poisoning: plunge a piece of gold into the intestine or tissues and see if a superficial amalgam forms. He also describes the colic, cramps, and discharge of blood from arsenic poisoning, and gives several antidotes including emetics.