Well, ketones need to be dealt with as soon as possible to avoid a potential medical emergency situation. Ketones will not spill over into the urine at first, so blood ketone measurement enables you to detect, and therefore treat, ketones quickly. Read this article on ketones by Gary Scheiner.
Meters available in the UK, with ketone test strips on prescription, include:
Your diabetes clinic is unlikely to object to the need for a blood ketone meter. If the GP refuses to provide blood ketone test strips because of their cost, ask the hospital-based diabetes specialist team to write to your GP to request the prescription.
Read more information about ketones, including the difference between low grade ketosis caused by a low-carb diet and diabetic ketoacidosis (DKA) at the Diabetes Self-Management website.