Although millions of people have used low-carb dieting without documented harm, there are some for whom a low-carb diet must be approached with caution.
If you are taking medication to control your blood sugar or blood pressure, you will need to quickly reduce the dosage and may need to discontinue these meds altogether if you significantly restrict your carbohydrate intake. This is best done under the supervision of a doctor.
For anyone who has serious kidney disease, an increase in dietary protein can be a problem. If you have kidney disease you should consult your doctor before making any changes to your diet.
Anyone who has any other serious illness such as unstable cardiovascular disease, cancer or liver disease need to exercise caution if making dietary changes. You should consult your doctor for guidance.