Please do not alter your medication or dosage on your own. Blood pressure medications like Losar (Losartan) can take two to four weeks to become fully effective; two days is simply not enough time. Since your blood pressure remains high (up to 160/110 mmHg), continue to monitor and record your readings twice daily. Contact your doctor to discuss these readings, as they may eventually need to adjust your treatment. Seek immediate emergency care if you experience severe headaches, chest pain, dizziness, or vision changes.