You should not use Humulin N if you are having an episode of low blood sugar.
Never share an injection pen or syringe with another person, even if the needle has been changed.
Hypoglycemia, or low blood sugar, is the most common side effect of Humulin N. Symptoms of low blood sugar may include headache, hunger, sweating, pale skin, irritability, dizziness, feeling shaky, or trouble concentrating. Watch for signs of low blood sugar. Carry a piece of non-dietetic hard candy or glucose tablets with you in case you have low blood sugar.
