How long does it take to go keto? It depends entirely upon your situation, your confidence, and what you want to achieve. Some people with Type1 diabetes seem to be able to achieve good control and at the same time eat a low-fat, high-carbohydrate diet. They do not seem to get complications with slightly higher Hba1c. Such people are probably happy the way they are and will not be looking to change things.
Then there are others who are keen to start as soon as possible because they feel their control is poor. It is up to the partnership between you and your clinician to work out how quickly the transition to a low-carbohydrate or ketogenic diet should happen. It is important to have a conversation with your specialist if you have complications with your diabetes. There are certain principles of managing the transition to a keto diet that you need to discuss. If your clinician is supporting you they can find this information on the Advanced Course. As a general rule, you will require a slow, managed tapering of carbs with regular reviews of your clinical state.
It is probably not helpful to emphasise the levels of ketones to aim for in Type 1 diabetes. Achieving high levels of ketones can become an aim in itself. It is not the prime aim. That is to achieve long periods of normal or near-normal blood glucose. We are emphasising the need to reduce carbohydrate intake so that the body primarily utilises fat for energy. So, because the end product of fat-burning is the production of ketones, the diet will be ketogenic by default. A survey of 120 people using a ketogenic diet done through this website found that 75% were in the blood ketone range of 0.5-1.5mmol/l. That seems modest when compared to some levels claimed on social media, but it likely reflects a typical level on a keto diet and a healthy ketone-burning state. Find out your own ketone levels over time and that is likely to be your normal. 0.5 or 2.5 mmol/l, whatever it is. There will be an individual range for every one of us. However, Type 1 control will at some point require glucose supplements to ensure the safe management of hypos, and sometimes the basal insulin dose might be less than ideal in times of stress and infection. The effect of stress hormones in raising blood glucose might throw you out of ketosis. It doesn’t matter. If you manage the basal insulin levels to the optimum and are confident in carbohydrate counting you should be able to achieve good blood glucose control and get to adequate nutritional ketosis within 2-3 weeks of starting a ketogenic diet. But equally, it is perfectly ok to go more slowly and reduce the carbohydrate in one meal at a time in a stepwise fashion over several weeks. You might for a start prefer to low carb just one meal at a time. It is individual. This is a lifestyle that you base around your requirements. Many people might not want to go to very low carbohydrate diets in the 30g a day range but prefer to use more carbohydrates.
The aim is to simply achieve near-normal blood glucose 24 hours a day. A keto diet will enable reduced insulin volumes which in the longer term is a good thing. It is not unrealistic to expect this with a lowered carbohydrate approach to dietary management.