Insufficient blood supply to the penis may be caused by bad life habits, or it may be caused by diabetes or genitourinary infections, penile cancer and so on. 1. Bad habits: Bad habits such as staying up late and drinking alcohol can lead to a decrease in blood sex hormones, which in turn leads to insufficient blood supply to the penile corpus cavernosum. 2. Diabetes mellitus: If diabetes mellitus exists for a long time, it will lead to atherosclerosis of the blood vessels in the cavernous part of the penis, which will narrow the blood vessels and lead to a gradual decrease in the blood supply to the cavernous part of the penis. 3. Genitourinary infections: Infections in the prostate gland and testicles may affect the secretion of sex hormones, resulting in insufficient blood supply to the penis. 4. Penile cancer: it is a malignant tumor originated from the head of penis and coronal sulcus, the cause of which is not clear yet, and it may be related to factors such as excessively long foreskin and bad hygienic habits, which can cause insufficient blood supply to the penis. Besides, there are many other reasons that can lead to insufficient blood supply to the penis, and one should pay attention to timely consultation to avoid delaying the condition.