The best replacement for osmolality is osmolarity.

The best alternatives to osmolality are rated as following:
★★★★★  osmolarity
★★★★  tonicity
★★  specific gravity
★★  molality
★  serum osmolality
  serum osmolarity
  serum sodium

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Speaking about osmolality, one probably shouldn't forget about hyponatremia.

Other search terms related to osmolality and their ratings are:
★★★★★ hyponatremia
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osmolality
osmolarity
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