The primary health concerns about LSD use are related to psychological health rather than risk of physical damage to the body or brain. As senior LSD researcher Dr. David Nichols, Distinguished Chair of Pharmacology at Purdue University and head of one of the world's top LSD research labs, stated in his 2004 review article on hallucinogens, "There is no evidence that any of the hallucinogens, even the very powerful semisynthetic LSD, causes damage to any human body organ. [...] Hallucinogens do not cause life-threatening changes in cardiovascular, renal, or hepatic function because they have little or no affinity for the biological receptors and targets that mediate vital vegetative functions."1 Deaths resulting from the pharmacological effects of LSD are rare to non-existent. -erowid

Less than a handful of deaths have been directly attributed in the medical literature to the pharmacological effects of LSD, and none of these have been unquestionably attributable to LSD's actions. Estimates of what could be a potentially lethal dose of LSD are higher than 10 mg orally, a dose that is more than 100 times the common, moderate dose of LSD (100 ug). The administration of this amount would require the ingestion of more than 200 units of street blotter, which typically contain about 50 ug of LSD (as of late 2010).

It is important to note that LSD has been associated with deaths as a result of inebriated behavior (falling from a height or fighting with police) or by suicide. There are also occasional deaths misattributed to LSD when another substance was actually taken.
-erowid

"Tusko" was also the name of a male Indian elephant at the Oklahoma City Zoo. On August 3, 1962, researchers from the University of Oklahoma injected (human use involves oral ingestion) 297 mg of LSD (lysergic acid diethylamide) to him, which is over 1,000 times the dose typical of human recreational use. Within five minutes he collapsed to the ground and one hour and forty minutes later he died. It is believed that the LSD was the cause of his death, although some speculate that the drugs the researchers used in an attempt to revive him may have contributed to his death.

1) I'm terrible at math

The administration of this amount would require the ingestion of more than 200 units of street blotter

PiHKAL Chapter 3 Burt
One morning, a couple of weeks later, I took a small, double-ended vial to Burt in his analytical lab down the hall, and asked him to please weigh out for me a small quantity of material into a separate container. The actual amount was not important, a few milligrams; what was important was that I wanted the weight accurate to four places. He disappeared for a few minutes, then reappeared with the vial I had given him and also a weighing container holding a small amount of an almost white powder. "Here is 3.032 milligrams, exactly," he said, adding, "And it's slightly bitter." "How do you know?" asked I. "After I weighed out the psilocybin, there was a trace of dust on the spatula, so I licked it off. Slightly bitter." I asked him, "Did you read the label carefully?" "It's the vial of psilocybin you just received, isn't it?" he asked, looking at the funny-shaped tube still in his hand. He read the label. It said Lysergide. He said, "Oh." We spent the next several minutes trying to reconstruct just how much LSD might have been on the end of the spatula, and decided that it was probably not more than a few score micrograms. But a few score micrograms can be pretty effective, especially in a curious but conservative analytical chemist who is totally drug naive. "Well," I said to him, "This should damned well be a fascinating day." And indeed it was. The first effects were clearly noted in about twenty minutes, and during the transition stage that took place over the following minutes, we wandered outside and walked around the pilot plant behind the main laboratory building. It was a completely joyful day for Burt. Every trivial thing had a magical quality. The stainless steel Pfaudler reactors were giant ripe melons about to be harvested; the brightly colored steam and chemical pipes were avant-garde spaghetti with appropriate smells, and the engineers wandering about were chefs preparing a royal banquet. No threats anywhere, simply hilarious entertainment. We wandered everywhere else on the grounds, but the theme of food and its sensory rewards continued to be the leitmotif of the day. In the late afternoon, Burt said he was substantially back to the real world, but when I asked him if he thought he could drive, he admitted that it would probably be wise to wait a bit longer. By 5:00 PM, he seemed to be happily back together again, and after a trial run -- a sort of figure-eight in the almost empty parking lot -- he embarked on his short drive home. Burt never again, to my knowledge, participated in any form of personal drug investigation, but he maintained a close and intimate interest in my research and was always appreciative of the slowly evolving picture of the delicate balance between chemical structure and pharmacological action, which I continued to share with him while I remained at Dole. One periodically hears some lecturer holding forth on the subject of psychedelic drugs, and you may hear him give voice to that old rubric that LSD is an odorless, colorless and tasteless drug. Don't believe it. Odorless yes, and colorless when completely pure, yes, but tasteless, no. It is slightly bitter. Transcribed from PIHKAL;shulgin

Here is 3.032 milligrams, exactly," he said, adding, "And it's slightly bitter." "How do you know?" asked I. "After I weighed out the psilocybin, there was a trace of dust on the spatula, so I licked it off. Slightly bitter." I asked him, "Did you read the label carefully?" "It's the vial of psilocybin you just received, isn't it?" he asked, looking at the funny-shaped tube still in his hand. He read the label. It said Lysergide. He said, "Oh."