Neem leaves' antihistamine properties might cause blood vessels to widen. This is why these leaves can aid in blood pressure reduction. A month of using neem extract or pills might also help decrease your elevated cholesterol levels. People with diabetes should not use neem because it can cause hypoglycemia (low blood sugar). People who are allergic to neem should not use it either. Side effects associated with neem use include dizziness, headache, nervousness, and skin rashes. For best results, take neem for one month or more to notice any improvements in blood pressure and cholesterol levels.