OBJECTIVE: To investigate the state of hydration in infants during the weaning period in dry and hot climates in the center of Iran. METHODS: Using a refractometer, 162 urine specific gravity (USG) was measured from 400 infants, between 4 to 6 months old. They were chosen among infants who visited the primary clinics in the city of Yazd, Iran for routine vaccination during the summer and winter of 2005. A questionnaire was filled out on air conditioning system and diet from mothers. A USG >1.020 was accepted as dehydrated, and a USG <1.010 as well hydrated. RESULTS: Thirty-one percent of the infants were dehydrated, and 34% were well hydrated, infants were more dehydrated in summer (p<0.05). Twenty-seven percent of them started solid food without water supplementation, and dehydration was significant in most of them (p<0.05). We could not determine which type of air conditioning devices now used at home affect water status, but there was a trend toward dehydration in those using both fan and cooler (p=0.096). CONCLUSION: In the desert area in the center of Iran, during weaning, approximately one third of the infants are exposed to the danger of dehydration. Our primary health care provider should consider the priority of water during weaning when water supplementation is safe. PMID: 19082227 [PubMed - indexed for MEDLINE