Someone in my family died in 1924 of type 1 diabetes at the age of 26. What would life have been like for her? Would she have been in the hospital frequently? What was the average life-expectancy for someone with type 1 diabetes back then?
Life for someone with diabetes in the early 20th century would be the same as someone with diabetes now if it was left untreated. The consequences of not treating diabetes include:
The discovery of insulin as a treatment for diabetes occurred in the 1920s, so either this family member was already suffering severe consequences of diabetes or she did not obtain sufficient treatment in time. Any treatments available before the discovery of insulin were only experimental.
On a related note, I found an article in the Diabetes journal that confirms msh210's comment that testing was done by tasting the urine.