Tammelin was born in Stockholm, Sweden and was the son of Supreme Court Justice Erik Tammelin and Elsa Palm. Tammelin, who was an organic chemist, was recruited to the Swedish National Defence Research Institute (FOA) in 1950 for research on nerve gas and nerve gas countermeasures. At this time, FOA (whose previous chemical warfare activities had focussed on mustard gas and other World War I-style compounds) had become aware that large quantities of nerve gas, primarily Tabun, had been stockpiled during World War II. The mechanism of action of the nerve gases were found to be linked to their chemical similarity to the neurotransmitter acetylcholine and their ability to block the enzyme cholinesterase. Much of Tammelin's work was therefore focussed on choline esters. In 1958, he defended a Ph.D. thesis based on this work at Stockholm University College. The esters that form the V-Series of nerve agents are sometimes referred to as "Tammelin's esters".
Succinylcholine, one of the compounds synthesized by Tammelin in his search for nerve gas countermeasures was put into use as a muscle relaxant for use during general anaesthesia surgery under the brand name Celocurin.
In 1961, Tammelin became head of the chemical-medical division at FOA, when he successed Gustaf Ljunggren. Tammelin became a medical honorary doctorate at Karolinska Institutet in 1973. He was professor and research director of the National Food Administration from 1975 to 1982 and director-general of FOA from 1984 to 1985.
In 1946 he married Isa Nilson (born 1922), the daughter of factory manager Nils Konrad Nilson and Sigrid Johansson.
- Burling, Ingeborg, ed. (1962). Vem är det: svensk biografisk handbok. 1963 [Who is it: Swedish biographical handbook. 1963] (in Swedish). Stockholm: Norstedt. p. 1058.
- Uddling, Hans; Paabo, Katrin, eds. (1992). Vem är det: svensk biografisk handbok. 1993 [Who is it: Swedish biographical handbook. 1993] (in Swedish). Stockholm: Norstedt. p. 1271. ISBN 91-1-914072-X.
- Larsson, Lennart (1995). Littke, Ann Kathrine; Sundström, Olle, eds. "Nervgasforskning under två decennier - en översikt" [Nerve gas research during two decades - an overview]. Försvarets forskningsanstalt 1945-1995 (in Swedish). Försvarets forskningsanstalt: 185–188. ISBN 91-87184-39-7.
- Lars-Erik Tammelin: Choline esters: substrate and inhibitors of cholinesterases, Diss., Stockholm, 1958. (LIBRIS record)
- Vem är det: svensk biografisk handbok. 1985 [Who is it: Swedish biographical handbook. 1985] (in Swedish). Stockholm: Norstedt. 1984. p. 1090. ISBN 91-1-843222-0.
- "Karolinska Institutet Medicine hedersdoktorer 1910‐2013" [Karolinska Institutet honorary doctors of medicine 1910-2013] (PDF) (in Swedish). Karolinska Institutet. Retrieved 4 April 2016.