Is it absolutely necessary to take off work for 2 weeks due to phlebitis?

See a phlebologist: Wear medical support stockings, ambulate 30 minutes a day, and listen to advise of primary doctor or phlebologist about blood thinners. All this will determine the time to settle the thrombophlebitis.

Compression & walkin: If you wear a 30-40 mmhg gradient compression stocking and take anti-inflammatory medication, you could walk and engage in nonstrenuous activity. I would avoid sedentary activity like sitting or standing in one place all day. You should follow up with your physician to have an duplex scan to make sure a deep vein blood clot does not form.