Numbers and thresholds

Diabetes

• Diagnosis: HbA1c 48 mmol/mol (6.5%) or more, fasting glucose 7.0 mmol/L or more, or random or 2-hour glucose 11.1 mmol/L or more. A single result is enough only with symptoms.
• Non-diabetic hyperglycaemia: HbA1c 42 to 47 mmol/mol.
• Hypoglycaemia: below 4 mmol/L.
• DKA: ketones above 3 mmol/L, venous pH below 7.3 or bicarbonate below 15 mmol/L, and glucose above 11 mmol/L or known diabetes.
• HHS: glucose 30 mmol/L or more and osmolality 320 mosmol/kg or more.
• Gestational diabetes: fasting 5.6 mmol/L or more, or 2 hours 7.8 mmol/L or more on the OGTT.

Electrolytes and kidneys

• Sodium: below 135 mmol/L is hyponatraemia; above 145 is hypernatraemia. Correct by no more than 10 mmol/L in the first 24 hours.
• Potassium: 5.5 to 5.9 mild, 6.0 to 6.4 moderate, 6.5 or more severe hyperkalaemia.
• Adjusted calcium: above 2.6 mmol/L is high, below 2.2 is low. Refer hypercalcaemia at 2.85 or more.
• AKI: a creatinine rise of 26 micromol/L or more within 48 hours, a rise to 1.5 times baseline within 7 days, or urine below 0.5 mL/kg/hour for more than 6 hours.
• CKD: eGFR G3a 45 to 59, G3b 30 to 44, G4 15 to 29, G5 below 15. ACR A2 is 3 to 30 mg/mmol, A3 above 30.
• Metformin: reduce the dose below an eGFR of 45, and do not start it below 30.

Blood

• Anaemia: haemoglobin below 130 g/L in men and below 120 g/L in non-pregnant women.
• In pregnancy: below 110 g/L in the first trimester, below 105 g/L after that, and below 100 g/L after the birth.
• Absent iron stores: ferritin below 15 micrograms/L (but ferritin rises with inflammation).
• Red cell transfusion: usually below 70 g/L, aiming for 70 to 90; in acute coronary syndrome, below 80 g/L, aiming for 80 to 100.
• Neutropenic sepsis: neutrophils 0.5 or lower with a temperature above 38 degrees or signs of sepsis.
• Vitamin D deficiency: below 25 nmol/L.

Heart and blood pressure

• Hypertension: clinic 140/90 or more, confirmed with ABPM or home readings of 135/85 or more. Stage 2 is 150/95 on ABPM. Severe is clinic systolic 180 or diastolic 120 or more.
• Targets: below 140/90 under 80 years, below 150/90 at 80 or over.
• NT-proBNP: above 2,000 ng/L, specialist assessment and echo within 2 weeks; 400 to 2,000, within 6 weeks.
• Ejection fraction: 40% or less is reduced, 41 to 49% mildly reduced, 50% or more preserved.
• QTc: over 450 ms is long, under 350 ms is short.
• Postural hypotension: a fall of 20 mmHg systolic or 10 mmHg diastolic within 3 minutes of standing.

Lungs

• COPD: FEV1/FVC below 0.7 after a bronchodilator. FEV1 50 to 79% moderate, 30 to 49% severe, below 30% very severe.
• Asthma (adults): FeNO 50 ppb or more, or a bronchodilator rise of 12% and 200 mL. In children aged 5 to 16, FeNO 35 ppb or more.
• Acute asthma: peak flow 33 to 50% is acute severe, below 33% life-threatening.
• Oxygen targets: 94 to 98% for most, 88 to 92% with a risk of hypercapnic failure.
• Pleural fluid: protein above 35 g/L is an exudate, below 25 g/L a transudate; 25 to 35 needs Light's criteria.

Scores

• NEWS2 in suspected sepsis: 7 or more high risk, 5 or 6 moderate, 1 to 4 low.
• CRB65: 0 manage at home; 2 or more consider hospital. CURB65: 3 to 5 is high severity.
• PE Wells: above 4 means PE is likely. DVT Wells: 2 or more means likely.
• CHA2DS2-VASc: offer anticoagulation at 2 or more, and consider it for men at 1.
• GCS: 8 or below, protect the airway.
• PHQ-9: below 16 is less severe depression, 16 or more more severe.
• AUDIT: 20 or more suggests possible dependence.

Children

• Fever traffic light (NICE): under 3 months, 38 degrees or more is red; 3 to 6 months, 39 or more is amber.
• Respiratory rate: over 60 is red. Over 50 at 6 to 12 months and over 40 over 12 months are amber.
• Bronchiolitis: oxygen when saturation is persistently below 92%; refer for apnoea or a respiratory rate over 70.
• Jaundice: visible in the first 24 hours means a serum bilirubin within 2 hours. Prolonged is beyond 14 days at term, 21 days preterm.
• Faltering growth: a fall across 2 or more centile spaces from a birth weight between the 9th and 91st centiles, or a weight below the 2nd centile.

Drugs and alcohol

• Alcohol: no more than 14 units a week, spread over 3 or more days. One unit is 10 mL or 8 g of alcohol.
• Lithium: 0.6 to 0.8 mmol/L, measured 12 hours after the dose.
• Paracetamol: treatment line at 100 mg/L at 4 hours. A potentially toxic dose is 75 mg/kg or more in 24 hours.
• Tricyclic overdose: QRS above 100 ms.

Cancer referral

• CA125: 35 IU/mL or more needs an urgent pelvic ultrasound.
• FIT: 10 micrograms of haemoglobin per gram of faeces or more means a suspected cancer referral.
• Postmenopausal endometrium: 4 mm or more on ultrasound needs a biopsy.