Can a diabetic patient go on a keto diet?
I'm going to assume you're referring to type 2 diabetics. Type 1's are a bit different and they may benefit from a ketogenic diet, but here's what I say for type 2's.
I'll go a little further and say not only "can" you do it. You should do it. I'll give you my anecdotal experience which will mirror the paper I'll link to later in this answer. I was watching my weight, trying to eat the low fat, healthy whole grain diet and injecting 60+ units of Lantus plus often using a short acting insulin with meals. My A1C was 9.0. I go on a low carb, healthy fat ketogenic diet. I need to taper down my insulin. I lose 35 pounds. Eventually, I drop all insulin and with taking metformin now have my blood sugars to a good for diabetic level in the 6.5 to 7 range.
OK you say, very nice anecdotal story, but do you have any science? Well, in fact there is science on this. First I suggest you read this article by Stephen Phinney. That article references a medical study done with 262 patients at the Indiana University Health Center. They were able to get 47.7% of these diabetics below the (good for diabetic) mark of 6.5 A1C with only the diabetes drug metformin. These people were like me and off other diabetic drugs other than metformin.
The people doing this science is an online diabetes management clinic called VirtaHealth. The great part of that approach is that they have physicians and counselors on staff. I took the ad lib approach but that worked out quite well for me.