Simvastatin is a medication used to lower cholesterol levels in the blood. As with any medication, there are potential side effects that you should be aware of. The most common side effects of simvastatin 40 mg include:

1.Muscle pain or weakness: This is the most common side effect of simvastatin, affecting up to 10% of users. In rare cases, it can lead to a condition called rhabdomyolysis, which can cause kidney damage.

2.Digestive problems: Simvastatin can cause diarrhea, constipation, nausea, and vomiting.

3.Headache: Some people may experience headaches while taking simvastatin.

4.Skin rash: Simvastatin can cause a rash or other skin reactions.

5.Liver problems: In rare cases, simvastatin can cause liver damage or liver failure.

6.Memory loss or confusion: Some people may experience memory loss, confusion, or trouble concentrating while taking simvastatin.

If you experience any of these side effects, you should contact your doctor right away. In some cases, your doctor may need to adjust your dosage or switch you to a different medication.