Quinine has many unwanted effects. It has bitter taste, and irritant to the gastric mucosa. Because of this, it may cause nausea and vomiting. High plasma concentration may cause cinchonism, which presents symptoms including nausea, dizziness, tinnitus,headach and vision blurring. It also can cause coma. Other rare side effects include blood dyscrasias. Blackwater fever, which is an acute haemolytic anaemia with renal failure is rare, but fetal.