Have you asked your diabetes educator nurse or dietitian about this? The answer to your question somewhat depends on how your diabetes is being treated (are you taking insulin, oral medication, or no medication?). In general, according to the Canadian Diabetes Association Clinical Practice Guidelines, the target blood sugar 2 hours after a meal is 5-8 mmol/L. So depending on how long after dinner you are testing your blood sugar, this target may help guide you. If your blood sugar is below 5 mmol/L, you may need to have a bedtime snack especially if you take certain diabetes medications. Having said that, many people have experimented with bedtime snacks and usually are able to determine whether a snack is needed based on experience. The main concern for people taking certain diabetes medication is low blood sugar (hypoglycemia) during the night. A person who doesn’t take diabetes medication usually doesn’t need a bedtime snack because they don’t run the risk of a low blood sugar.
I would recommend you talk to your physician or diabetes education team about what is the best blood sugar for you before bedtime.