Hyperosmolar hyperglycaemic state

HHS (formerly known as HONK or hyperosmolar non ketotic coma) is the typical hyperglycaemic emergency of type 2 diabetes. It is characterised by hyperglycaemia and significant hyper osmolality (serum osmolality, calculated as 2xNa+glucose, of greater than 320 mOsmol/kg) in the absence of significant ketosis.

Assessment of ketosis

The urine should be dipped for ketones to check that there isn’t co-existent DKA or that the nature of the hyperglycemia isn’t predominantly keto-acidotic.

Usually, in straightforward HHS, the urinary ketones will be less than 2+.

Acid base status

Blood gases should be assessed in order to check that the primary diagnosis isn’t actually DKA.

In addition, the patient should be assessed for a lactic acidosis which may arise due to severe tissue hypo-perfusion and/or due to metformin accumulation.


This is part of the 'septic screen' and also an important baseline. 


This is essential in order to assess the baseline K+ as well as giving a biochemical indication of dehydration and of renal function.


Laboratory glucose is an essential baseline investigation.


Although not directly relevant to the management of HHS, it is a useful opportunity to assess the overall level of glycaemic control.


A useful baseline.


This is usually performed as part of the 'septic screen'.


The presence of nitrites, leukocytes, protein and blood should prompt a sample being sent for microscopy, culture and sensitivity.

Blood cultures

These should also be sent if there is suspicion that there is a septic precipitant of the episode.

Cardiac enzymes

Troponin and CK should be checked in order not to miss a 'silent' MI which may have precipitated the HHS.


ECG should be checked in order not to miss a 'silent' MI which may have precipitated the HHS.


Osmolality should be calculated as 2xNa+glucose, sometimes 2xK+, is also included but this contributes very little to the total.

Urea, strictly speaking, should not be included in the calculation as it is freely diffusable between fluid compartments. Normal serum osmolality is between 285 and 295 mOsmol/Kg.

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