Consuming 3 to 4 bottles of codeine cough syrup daily is highly unsafe. This excessive amount poses severe health risks, including respiratory depression and addiction. Furthermore, cough syrups typically contain high levels of sugar or alcohol, which are likely contributing significantly to your elevated fasting (140 mg/dL) and post-meal (260 mg/dL) blood sugar levels. Because your blood sugar is poorly controlled and high doses of codeine are dangerous, please consult your doctor or seek immediate medical guidance. They can help you safely manage your blood glucose and assist with a safe plan to reduce and stop the syrup.