What is the empirical price elasticity of demand for insulin? A lot of textbooks say that demand for insulin is perfectly inelastic. I don’t think this is quite true (and I am a type 1 diabetic). It’s clearly very inelastic, but not perfectly so. There are things you can do to reduce your insulin intake, e.g. eat less carbohydrates.
I’m curious if any studies have actually gone out and measured this…
You are right! Textbooks are probably not careful enough.
However, there is evidence that the most inelastic drugs are those indicated for the treatment of chronic diseases with price-elasticity ranging form -0.08 to -0.03 [see here], while studies establish a general inelastic price-elasticity of drugs of around -0.2 (here). In the same Plos One paper, therapeutic groups are sorted by price-elasticity and the diabetes group is ranked third behind cardiovascular and endocrine diseases (see Figure 1).