Recently, four studies have re-examined the effect of carbohydrate restriction on type 2 diabetes. One outpatient study enrolled 54 participants with type 2 diabetes (out of 132 total participants) and found that hemoglobin A1c improved to a greater degree over one year with a low-carbohydrate diet compared with a low-fat, calorie-restricted diet [5,6]. Another study enrolled 8 men with type 2 diabetes in a 5-week crossover outpatient feeding study that tested similar diets [7]. The participants had greater improvement in glycohemoglobin while on the low-carbohydrate diet than when on a eucaloric low-fat diet. The third study was an inpatient feeding study in 10 participants with type 2 diabetes [8]. After only 14 days, hemoglobin A1c improved from 7.3% to 6.8%. In the fourth study, 16 participants with type 2 diabetes who followed a 20% carbohydrate diet had improvement of hemoglobin A1c from 8.0% to 6.6% over 24 weeks [9]. Only these latter three studies targeted glycemic control as a goal, and two of these were intensely-monitored efficacy studies in which all food was provided to participants for the duration of the study [7,8]. Three of the studies [6,8,9] mentioned that diabetic medications were adjusted but only one of them provided detailed information regarding these adjustments [9]. This information is critical for patients on medication for diabetes who initiate a low-carbohydrate diet because of the potential for adverse effects resulting from hypoglycemia.
Aude, Y., A. S, Agatston, F. Lopez-Jimenez, et al. “The National Cholesterol Education Program Diet vs a Diet Lower in Carbohydrates and Higher in Protein and Monounsaturated Fat: A Randomized Trial.” JAMA Internal Medicine 164, no. 19 (2004): 2141–46. doi: 10.1001/archinte.164.19.2141.
^ Another publication of similar regimen was Hill LW, Eckman RS (1915). The Starvation Treatment of Diabetes with a series of graduated diets as used at the Massachusetts General Hospital. Boston: W.M. Leonard. This was so well received that it went into revised editions, eventually becomingThe Allen (Starvation) Treatment of Diabetes with a series of graduated diets (4th ed.). Boston. 1921. p. 140.

I have been on a keto diet for over a year. I lost 60 pounds and got off five different meds and a shot in the stomach for the last 25 years. Fasting sugar under 150 was considered good control. A1C was usually around 7. Now sugars are rarely over 80 and A1C is 5.4. THEN I PLATEAUED AND EVEN GAINED BACK 10 pounds. Little did I know I have been shooting myself in the foot. It didn't help that I quit a job that required seven miles of vigorous walking each day, but I begin my day with a big glass of half and half. I didn't realize I was adding 16-20g hidden carbs over my 25g allotment. I am switching to making my own with heavy whip cream and almond milk. That drops carb count to 6.4g per cup.
Protein: When people first reduce carbohydrates in their diets, it doesn't seem as though the amount of protein they eat is as important to ketosis as it often becomes later on. For example, people on the Atkins diet often eat fairly large amounts of protein in the early stages and remain in ketosis. However, over time, some (perhaps most) people need to be more careful about the amount of protein they eat as (anecdotally) the bodies of many people seem to "get better" at converting protein into glucose (gluconeogenesis). At that point, each individual needs to experiment to see if too much protein is throwing them out of ketosis and adjust as necessary.
Ketogenesis results in the production of ketone bodies, a product of fatty acid catabolism performed primarily by the liver, in the absence of adequate CHO availability. Three primary ketone bodies are produced; acetone, acetoacetate and β-hydroxybutyrate. Even though trace amounts of ketones are always present in the blood, it is only during periods of inadequate CHO availability that significant ketone production will occur. This accumulation of ketone bodies in the blood is commonly referred to as ketosis.
In the first week, many people report headaches, mental fogginess, dizziness, and aggravation. Most of the time, this is the result of your electrolytes being flushed out, as ketosis has a diuretic effect. Make sure you drink plenty of water and keep your sodium intake up.6One of the fathers of keto, Dr. Phinney, shows that electrolyte levels (especially sodium) can become unbalanced with low carb intake.