Leptin

ND-recommended test reviewed: leptin.
Indications reviewed: weight gain, appetite concerns; no features of a pediatric congenital leptin deficiency syndrome present.
Not ordered. Rationale discussed: no validated role for leptin testing in adult primary care; the one recognized indication is a rare pediatric genetic condition. Ref: Mazen et al 2023, congenital leptin/leptin receptor deficiency.
Patient informed test available privately via ND. Patient given info page: https://labs.ajaxharwoodclinic.com/leptin/patient
Revisit if: new severe, early-onset obesity in a child with a family history suggestive of a genetic obesity syndrome.

Indicated when

• —Severe obesity beginning in infancy or early childhood with suspected congenital leptin or leptin-receptor deficiency: a rare, treatable condition diagnosed by pediatric specialists [1]

Not indicated when

• —Investigating fatigue, weight gain, difficulty losing weight, or appetite concerns in adults seen in primary care; leptin testing has no established role in this setting
• —Routine addition to a metabolic or hormone panel

Why not

Leptin has no established role in evaluating fatigue, weight gain, or appetite in typical adult patients seen in primary care. Its one clearly validated use, diagnosing congenital leptin or leptin receptor deficiency, is a specific pediatric condition presenting with severe, early-onset obesity from infancy, worked up by pediatric endocrinology or genetics rather than by ordering a leptin level in a family practice for an adult with ordinary weight concerns [1].

Better first step

For weight or appetite concerns in an adult, a focused history (diet, activity, sleep, medications, mood) and standard metabolic bloodwork are the appropriate first steps; a leptin level does not add usable information in this setting.

Typical ND rationale

An ND may order leptin reasoning that it is a hormone made by fat tissue that signals fullness to the brain, so measuring it could help explain why a patient feels hungry, gains weight easily, or has treatment-resistant weight gain.

Ontario coverage & CONO orderability

OHIP status

uninsured

Leptin does not appear by name anywhere in the 2026 Schedule of Benefits for Laboratory Services, consistent with docs/research/ontario-coverage.md's listing of leptin among tests absent from the community Schedule. Absence from the community Schedule doesn't rule out coverage through another pathway, so this is recorded as unverified. ND-ordered testing is patient-paid regardless (Reg. 552 s.22). Coverage update (reconciliation pass): LifeLabs' Non-OHIP Billable Test List (2025, republished by an Ontario hospital lab) lists this test as patient-paid in community labs. This is secondary evidence, not a ministry statement.

CONO orderable

Yes — CONO list #87

CONO list item 87, blood: 'Leptin.'

Linked conditions

• tired ↗

Counselling script

“Leptin doesn't have a proven role in explaining weight gain or appetite in adults, so checking it wouldn't change what we do next. The one condition where it matters, a rare genetic leptin deficiency, shows up as severe obesity starting in infancy and is worked up by specialists. Let's instead look at your diet, sleep, activity, and standard bloodwork, which will actually guide what we do.”

Revisit if

• —New concern for a pediatric genetic obesity syndrome (severe, early-onset obesity with an increased appetite in a child)
• —New clinical features suggesting an endocrine cause of weight change

References

1. [1]Molecular Genetics and Genomics (Mazen et al.) (2023). Congenital leptin and leptin receptor deficiencies in nine new families: identification of six novel variants and review of literature. linkLeptin measurement is useful for diagnosing congenital leptin and leptin receptor deficiency, a rare cause of severe early-onset obesity
2. [2]Ontario Ministry of Health (2026). Ontario Health Insurance Plan: Schedule of Benefits for Laboratory Services (effective April 1, 2026). linkCommunity lab tests are insured only when ordered under the Schedule by an authorized prescriber
3. [3]Government of Ontario (e-Laws) (2026). Health Insurance Act, R.R.O. 1990, Reg. 552: General, s. 22 (insured laboratory services). linkA lab test is insured only when ordered by a physician, midwife, or NP who has clinically assessed the patient
4. [4]Ontario Ministry of Health (2026). Ontario Health Insurance Plan: Schedule of Benefits for Laboratory Services (effective April 1, 2026). linkTests ordered by anyone other than an authorized provider, including NDs, are not insured services
5. [5]LifeLabs (republished by Norfolk General Hospital laboratory) (2025). LifeLabs Non-OHIP Billable Test List (republished by Norfolk General Hospital laboratory, effective 2025). linkListed as a non-OHIP (patient-paid) test at LifeLabs Ontario, 2025