What does coughing up yellow phlegm indicate?

Yellow phlegm: Yellow phlegm may indicate infection of the upper respiratory tract. Of course some slightly tinged yellow phlegm may be normal when you fist wake up. When it is persistent or when there is associated fevers and chills, it may signify a bacterial or viral infection. Most infections will clear on their own and do not always require antibiotics. If these symptoms last longer than 5-7 d see doc