In the UK, the title "dietitian" can only be used by a person who has qualified with a degree in nutrition and dietetics and who has been granted state registration by the Health Professions Council. A dietitian will translate scientific information about food into practical dietary information and advice. The dietitian will advise about food-related problems, treat food-related diseases and ill health, and provide practical advice tailored to your lifestyle and specific nutritional requirements.
By contrast, anyone is able to call themselves a nutritionist, regardless of their background or qualifications, and use of this title is unregulated. Nutritionists are often seen as alternative health practitioners and may give dietary advice together with a range of nutritional supplements. They may also carry out allergy tests to diagnose nutritional problems. Their approach is not necessarily based on clinical scientific evidence.