IRCT20120215009014N299 IRCT 2019-09-23 Hamedan University of Medical Sciences Effect of melatonin supplement versus placebo on the severity of pain, sleep disorder, and quality of life in patients with painful diabetic neuropathy Effect of melatonin supplement versus placebo on the severity of pain, sleep disorder, and quality of life in patients with painful diabetic neuropathy: a double-blind randomized clinical trial 2019-09-23 anticipated 116 Complete https://irct.ir/trial/42048 interventional Randomization: Randomized, Blinding: Double blinded, Placebo: Used, Assignment: Parallel, Purpose: Treatment, Randomization description: The patients will be randomly assigned to intervention and control groups using block randomization. For this purpose, we will prepare four sheets of paper, writing on two sheets the name of the intervention and on the other two sheets the name of the control. The paper sheets will be pooled, placed in a container, and randomly drawn one at a time for each patient without replacement until all four sheets are drawn. The four paper sheets will be then placed back into the container, and this action repeated until the sample size is reached, Blinding description: The shape of the medications and placebos will be perfectly the same. Therefore, patients will be unaware of the type of intervention. The physician who will examine the patients will not be aware of the intervention. Thus, the trial will be run as double-blind. 2 Painful diabetic neuropathy. Intervention 1: Intervention group: Tablet pregabalin 75 mg daily plus tablet melatonin 6 mg twice daily for 8 weeks. Intervention 2: Control group: Tablet pregabalin 75 mg daily plus tablet placebo twice daily for 8 weeks. Undecided - It is not yet known if there will be a plan to make this available Justification or reason for indecision in sharing IPD is It depends on the situations and the results of the study as well as approval of the financial supporting organization.