<s>[INST] I am female 52 years. Suffer ulcerative colitis and awaiting knee replacement.Why do i have cold shivers that last for a couple of hours and feel totaly washed out.It used to happen now and again but has happened three times this week. Today1.30pm and I am only now feeling a bit betterat 10pm [/INST] Hello!Welcome on Healthcaremagic!Your symptoms could be related to a metabolic disorder (vitamin B12 or vitamin D deficiency, an electrolyte imbalance, thyroid gland dysfunction, etc.). Anxiety or Epilepsy seizures can not be excluded either. Coming to this point, I would recommend consulting with your GP for a physical exam and some tests: - complete blood count for anemia- thyroid hormone levels - blood electrolytes- vitamin D and vitamin B12 plasma levels- a resting ECG. An EEG may be needed if suspicions of seizures are raised. Hope you will find this answer helpful!Kind regards, Dr. Aida </s>