Factitious Hypoglycaemia

Factitious hypoglycaemia is hypoglycaemia caused by covert, self-administered insulin or insulin secretagogues (sulphonylureas, meglitinides). In children it may be due to a carer inducing illness.

It is more common in health professionals, people with access to insulin or sulphonylureas through family or work, women, and people with psychiatric illness or eating disorders.

Pathophysiology.

Exogenous insulin causes hypoglycaemia with high insulin and suppressed C-peptide and proinsulin, because endogenous secretion is switched off.

Sulphonylureas and meglitinides cause hypoglycaemia with high insulin, C-peptide and proinsulin, mimicking insulinoma.

• Recurrent unexplained hypoglycaemia in a person without diabetes, often severe and at unusual times.
• Inconsistent history, normal imaging and absence of other cause.

Red flags.

• Access to insulin or sulphonylureas at home or work, or a health care background.
• Unexplained hypoglycaemia in an infant or child, or repeated hospital attendance.
• Psychiatric history or evasive behaviour.

• Critical sample at spontaneous hypoglycaemia (glucose under 3.0 mmol/L or 54 mg/dL): glucose, insulin, C-peptide, proinsulin, beta hydroxybutyrate and sulphonylurea and meglitinide screen by mass spectrometry. Preserve samples.
• Endogenous insulin excess (insulinoma or secretagogue): insulin 3 microunits/mL (18 pmol/L) or more, C-peptide 0.6 ng/mL (0.2 nmol/L) or more, proinsulin 5 pmol/L or more, beta hydroxybutyrate 2.7 mmol/L or less, and glucose rise of 1.4 mmol/L (25 mg/dL) or more after glucagon.
• Exogenous insulin: high insulin, suppressed C-peptide (under 0.2 nmol/L) and proinsulin, insulin to C-peptide molar ratio over 1, and low beta hydroxybutyrate. Some analogue insulins (aspart, lispro, glargine, detemir, degludec) are poorly detected by some insulin assays, so low or normal measured insulin with suppressed C-peptide still suggests exogenous insulin; ask the laboratory.
• Sulphonylurea: positive drug screen with raised C-peptide.
• A supervised 72-hour fast and imaging only if insulinoma remains possible.

Differential diagnosis.

• Insulinoma and insulin autoimmune syndrome.
• Non-islet cell tumour hypoglycaemia.
• Post-bariatric hypoglycaemia, adrenal insufficiency, hypopituitarism, liver failure and sepsis.
• Inborn errors of metabolism in children.

• Treat hypoglycaemia: 15 to 20 g oral glucose, or intravenous 10% glucose 150 to 200 mL over 15 minutes (or 20% glucose 75 to 100 mL).
• Sulphonylurea poisoning: intravenous glucose and octreotide 50 micrograms subcutaneously or intravenously every 6 hours until stable. Observe for at least 24 hours and longer with glibenclamide or kidney impairment.
• Exogenous insulin: observe until insulin levels fall, up to 24 hours or more with long acting insulin.
• Disclose the findings privately, calmly and without accusation, with a psychiatrist or psychologist present where possible. Offer psychiatric assessment and treatment.
• Remove access to the agent where possible.

Special groups. Children: unexplained hypoglycaemia with a carer related cause is a safeguarding matter. Involve the safeguarding lead at once. Health professionals: involve occupational health and the regulator as the law and policy require.

Monitoring. Glucose and clinical follow up, with psychiatric review for relapse risk.

Referral and escalation. Psychiatry, safeguarding services and endocrinology.