First the nurse would need to determine if the yogurt had sugar in it. Many yogurts have artificial sweeteners or come without sweetener. You cannot assume the glycemic load just because it's yogurt. Assumption is the enemy of good patient care. You must get all the facts. There is too much information missing to give a reasonable answer. Has the client already tested their blood sugar in the morning before breakfast? Are they on insulin, and oral diabetes medication, or are they diet-controlled? Are they in an acute state of illness? The scenario needs many more details to adequately answer the question.