Once a cold/flu has moved to lungs, is it necessary to see a dr? what are the indicators that a dr needs to be seen and what treatment is there?

Maybe: If your cold has moved to your lungs so that you have are coughing up phlegm, then that is significant. If also you have a fever (temp 101 or more), then you should see a doctor. If also you have shortness of breath, especially if accompanied by fatigue, then go to emergency. Young people are often strong enough to keep going until their pneumonia is life-threatening, so better safe than sorry.

See below: During the cold and flu season the indications for patients with a cough to see a physician would include: -Fever >103 F -Fever>101 F accompanied by chills and coughing up greenish foul smelling sputum -Cough with fever and shortness of breath, chest pain with inspiration or coughing up blood -Fever of 100 or more lasting more than 4 days