Question: Does being on doxycycline make diagnosis more difficult or impossible?
Answer: It is possible to diagnose malaria while taking doxycycline – if you are experiencing symptoms, then there are usually enough malaria parasites in your blood to be detected via rapid diagnostic test, or seen through a microscope via a blood smear.
If you continue to take doxycycline while experiencing symptoms at the dosage prescribed for prophylaxis, while it may have some impact on the disease and make you feel slightly better, it is unlikely that you will be able to treat the infection completely, and you could put yourself at risk of recrudescence (where the malaria infection comes back within a few weeks of the initial infection, because it was not cleared completely from the body the first time).
Low dose treatment can also contribute to the malaria parasite developing resistance against doxycycline. As such, if you start to experience malaria symptoms (fever, aches, etc – see our full page on malaria symptoms here), it is very important that you seek medical attention as soon as possible, and that you tell them you have been taking doxycycline.
If your malaria test is positive, the medical practitioner will almost certainly provide you with a different medication for treatment, likely an artemisinin-based combination therapy.