I'm a bit concerned and would like some advice. I had COVID back in May and recovered at home with a mild case of lung pneumonia. I was on blood thinners at the time but stopped after my D-Dimer results returned to normal. Since recovering, I haven't had a cough or cold, but I sometimes notice black streaks in my phlegm, usually just once in the morning. I already spoke with a pulmonologist who told me to get a CBC and chest X-ray; everything came back normal. He said a CT isn't needed unless I start coughing, which I haven't. Is it common to have these black streaks in phlegm after COVID? At what point should I be concerned, and do you think I need any further tests? Here's a picture for reference. What do you think?

The presence of black streaks in phlegm, especially in the morning, can be a common post-COVID-19 symptom, possibly due to lingering inflammation, mucus, or fungal growth, and since your CBC, chest X-ray, and previous D-Dimer tests are normal, your pulmonologist's advice to monitor and not pursue further testing unless symptoms worsen or new ones develop is reasonable; however, if you experience increased frequency, thickness, or color change of the phlegm, difficulty breathing, chest pain, or fever, seek immediate medical attention to rule out potential complications like pulmonary embolism, bronchiectasis, or opportunistic infections.