Background: Low carbohydrate diet (LCD) has been effective for type 2 diabetes mellitus (T2DM), because of less post-prandial increase of blood glucose. Case presentation: The case is 62-year-old male with T2DM, who had experience of LCD a few years ago. He developed diabetic exacerbation as HbA1c 10.7% in autumn 2021. Results: He began super-LCD with 12% of carbohydrate in calorie ratio, and recorded the pictures of detail food intake every day and 45-minunte post-prandial blood glucose for long. His HbA1c decreased to 7.1% for 9 weeks. For breakfast, carbohydrate amount varies from 19.7 g to 51.1g, and 45-min post-prandial blood glucose distribute 121mg/dL to 226mg/dL. The relationship between carbohydrate amount in breakfast and 45-min post-prandial blood glucose was investigated. As a result, significant correlation was observed between them (R2=0.46, p
