Thanks for posting on HCM
UTI usually complicates diabetes
and can cause high sugar level to persist despite the original insulin
shots. Most of the diabetes at your husband's age are insulin resistant ( type 2) and his insulin type might need to be changed or dosage increased to doses that can control the sugar to normal level.
The UTI will have to be treated despite culture showing no significant growth.
Do get an appointment immediately with your doctor as your husband's situation may got worst.
Sugar control and UTI treatment is essential for your husband's survival.
Hope this heps