Levemir 100IU/ml Flexpen is a long-acting type of insulin used to treat types 1 and 2 diabetes mellitus in both adults and children. It provides a steady level of insulin in the body for an entire day and helps control blood sugar levels. This helps to prevent complications of diabetes. Levemir 100IU/ml Flexpen can be prescribed by itself or along with a fast-acting type of insulin or other diabetes medicines. Your doctor or nurse will teach you the correct way of injecting it under the skin. You should use this medicine regularly as per the dose advised to get the most benefit. If you stop taking it your blood sugar levels may rise very high and put you at risk of serious complications. It is only a part of the treatment program that should also include a healthy diet, regular exercise, and weight reduction as advised by your doctor.The most common side effect of this medicine is low blood sugar levels (hypoglycemia). To prevent this, it is important to always inject the correct dose of medicine only, have regular meals, and monitor your blood sugar levels regularly. Drinking excessive alcohol can also lead to a fall in your blood sugar levels. Other side effects include allergy at the injection site like redness, swelling, or pain. Some people may even gain weight while taking insulin.Do not use this medicine when you have low blood sugar levels (hypoglycemia). Tell your doctor if you have ever had kidney, liver or heart problems before starting treatment. It is generally regarded as safe for pregnant and breastfeeding women, if it has been prescribed by a doctor.