Why do I have erection problems despite normal total testosterone?

It could be due to free testosterone — its inactive form that is bound to proteins, and it is the free fraction that affects erections and libido. In a study, men with low free testosterone were more likely to have problems, even when total testosterone was normal. Ask your doctor to check free testosterone using a direct method rather than a calculated one, as formulas may underestimate the real picture. However, note that this study showed an association but not causation, and only a specialist can make a final diagnosis.