Can d dimer be used to rule out dvt/pe about 12 days after event ? long car ride 12 days ago with progressing symptoms. are is the 12 days too late and d dimer many be normal despite possible clot ?

If you have symptoms, you need to get a scan of legs or chest regardless of d-dimer. Please get seen in person.

A D-dimer test is more useful to exclude DVT/PE than diagnosing one. The test would not provide meaningful information 12 days after the incident. You did not state your symptoms, so it is not feasible to provide a more meaningful opinion. Wish you good health!