In clinically suspected DVT or PE, treatment with low-molecular-weight heparin (LMWH) should be commenced immediately until the diagnosis is excluded by objective testing, unless treatment is strongly contraindicated.

Compression duplex ultrasound should be undertaken where there is clinical suspicion of DVT.
If ultrasound is negative and there is a low level of clinical suspicion, anticoagulant treatment can be discontinued.

If ultrasound is negative and a high level of clinical suspicion exists, anticoagulant
treatment should be discontinued but the ultrasound should be repeated on days 3 and 7.

Intravenous unfractionated heparin is the preferred, initial treatment in massive PE with cardiovascular compromise.