Long-term care (LTC) residents, especially the orally fed with dysphagia, are prone to dehydration. The clinical consequences of dehydration are critical. The validity of the common laboratory parameters of hydration status is far from being absolute, especially so in the elderly. However, combinations of these indices are more reliable. Assessment of hydration status among elderly LTC residents with oropharyngeal dysphagia. A total of 28 orally fed patients with grade-2 feeding difficulties on the functional outcome swallowing scale (FOSS) and 67 naso-gastric tube (NGT)-fed LTC residents entered the study. The common laboratory, serum and urinary tests were used as indices of hydration status. The results were considered as indicative of dehydration and used as 'markers of dehydration', if they were above the accepted normal values. The mean number of dehydration markers was significantly higher in the FOSS-2 group (3.8 +/- 1.3 vs. 2 +/- 1.4, p = 0.000). About 75% of these FOSS-2 patients had > or =4 dehydration markers versus 18% of the NGT-fed group (p = 0.000). A low urine output (<800 ml/day) was significantly more common in the FOSS-2 group (39 vs. 12%, p = 0.002). Above normal values of blood urea nitrogen (BUN), BUN/serum creatinine ratio (BUN/S(Cr)), urine/serum osmolality ratio (U/S(Osm)), and urine osmolality U(Osm), were significantly more frequent in the dehydration-prone FOSS-2 group. This combination of 4 indices was present in 65% of low urine output patients. In contrast, it was present in only 36% of the higher urine output patients (p = 0.01). Patients with a 'normal' daily urine output (>800 ml/day) also had a significant number (2 +/- 1.5) of positive indices of dehydration. Dehydration was found to be common among orally fed FOSS-2 LTC patients. Surprisingly, probable dehydration, although of a mild degree, was not a rarity among NGT-fed patients either. The combination of 4 parameters, BUN, BUN/S(Cr ), U/S(Osm) and U(Osm), offers reasonable reliability to be used as an indication of dehydration status in daily clinical practice. Copyright 2007 S. Karger AG, Basel.