Can deep vein thrombosis come on in minutes, or does it build up over months?

Either can be true.: Dvt more commonly occurs in patients who have some risk factors, such as trauma, history in the family (possible predisposing that person to dvt- for example hereditary thrombophilia) or immobilization, due to obesity, inactivity or injury (casts, bedrest, illness, dehydration and others). It is less likely, but not impossible, to occur in minutes.

Usually quick: Some with congenital issue , left iliac vein compression etc , ay occur over time. A lot can also extend over time. The setting of trauma, stasis, coagulopathies.Is when we think of DVT along with cancer, obesity, surgery, birth control pills etc.

Dvt: Usually dvt is an acute process with sudden development of a clot and as it is forming will move forward