Calculators · Endocrinology · Criteria
Effective osmolality and DKA / HHS classification (ADA 2024)
Also called effective osmolality, tonicity, DKA criteria, HHS criteria, hyperglycaemic crisis
Effective osmolality and the 2024 ADA/EASD/JBDS/AACE/DTS criteria for DKA (with severity) and HHS.
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Formula and scoring
Effective osmolality = 2 × Na + glucose (mmol/L). Total = 2 × Na + glucose + urea (mmol/L). DKA severity: mild pH > 7.25–< 7.30, HCO₃ 15–18; moderate pH 7.0–7.25, HCO₃ 10–< 15; severe pH < 7.0, HCO₃ < 10 or β-OHB > 6.0.
Exam and ward pearls
- 2024 consensus lowered the DKA glucose threshold to 200 mg/dL and accepts known diabetes at any glucose — euglycaemic DKA with SGLT2 inhibitors.
- Urea is excluded from effective osmolality because it crosses cell membranes freely.
- Over one-third of hyperglycaemic crises show overlapping DKA and HHS features.
When not to rely on it
- For adults; children follow ISPAD criteria.
- Use measured (not corrected) sodium in the osmolality formula.
Source
- Umpierrez GE, Davis GM, ElSayed NA, et al. Hyperglycemic crises in adults with diabetes: a consensus report. Diabetes Care. 2024;47(8):1257-1275. Figure 2 and Table 2. doi:10.2337/dci24-0032 · PMID 39052901
Formula and cut-offs checked against these sources on 8 Nov 2026. Educational tool for clinicians; it does not replace clinical judgement.