What is the major side effect of insulin?
Hypoglycemia (low blood sugar) is the most common insulin side effect. This is when your blood sugar drops below 70 mg/dL. Having blood sugar this low can feel like any of these symptoms: Shakiness or tingling. Serious side effects Insulin can sometimes cause severe hypos, where your blood glucose falls very low and you can become unconscious. Speak to your doctor or diabetes nurse if: you’ve had severe hypos.