1. Blood Clots Can block a blood vessel
Also known as a thrombus or emboli

2. Diabetes Long term high blood sugar levels can damage blood vessels
This can cause weakening and narrowing of the blood vessel
Frequently have hypertension and hyperlipidemia which accelerates atherosclerosis

3. Inflammation of the arteries
Arteritis causes narrowing and weakening of the arteries
Vasculitis causes inflammatory injury and necrosis of the blood vessel wall

4. Infection
Inflammation and scarring caused by infection can block, narrow, or weaken blood vessels
Salmonellosis and syphilis are both known to infect and damage blood vessels

5. Structural Defects Defects can narrow a blood vessel
Most cases are cause a birth
Takayasu is a vascular disease affecting the upper vessels usually in Asian females

6. Injury
Blood vessels can be injured in accidents such as auto accidents and falls.