A blood sugar level of 338 is quite high and should not be ignored because uncontrolled diabetes can damage the eyes, kidneys, nerves, and heart over time. You should consult a doctor as soon as possible for proper evaluation and treatment. The required medicine depends on whether you have diabetes already, your fasting and post-meal sugar levels, HbA1c value, age, weight, and other medical conditions. Some people may need tablets, while others may require insulin if the sugar level is very high or if symptoms like excessive thirst, vomiting, weakness, or weight loss are present. Until you see a doctor, avoid sugary foods and sweet drinks, drink enough water, eat balanced meals, and monitor your blood sugar regularly. Seek urgent care if you develop confusion, breathing difficulty, or severe weakness.