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Levothyroxine

Pregnancy & gynaecology-specific. Every dose row is source-referenced; verify against institutional protocols.

LevothyroxineThyroid hormone replacement

Regimens checked: 2026-10-17. Each indication has its own preparation, limits and safety checks.

Levothyroxine: indication-specific regimens
IndicationDoseRouteFrequencyDuration / preparationMaximumMonitoring / cautions
Already receiving replacement before pregnancy
At positive pregnancy test increase the weekly dose by about 25–30%, e.g. double the usual daily dose on two days each week; then titrate to TFTs
Oral
Daily, with a clearly written seven-day dose schedule
Through pregnancy; make an individual postpartum dose plan and repeat TFTs about 6 weeks after birth · Use the prescribed microgram-strength tablets consistently before breakfast; separate oral iron/calcium by 4–5 hours. Micrograms are not milligrams
  • Pre-existing adequately treated disease generally returns to the preconception dose after birth according to the RCOG postpartum plan; reassess rather than automatically stopping permanent replacement.
No universal fixed maximum: titrate to pregnancy-specific TFTs; the initial 25–30% rise is not an instruction for repeated weekly increases
Monitor
  • TSH/FT4 every 4–6 weeks to 20 weeks and again at 28 weeks; target TSH <2.5 mIU/L with FT4 in the pregnancy reference range
Contraindications / cautions
  • Untreated adrenal insufficiency requires assessment/treatment; avoid overreplacement in cardiac disease
RCOG: overt hypothyroidism or TSH >10 mIU/L; distinguish milder subclinical disease
Overt/severe disease: 1.6 micrograms/kg/day initial replacement. For selected subclinical disease with TSH above the gestational range but ≤10, consider 1.0–1.2 micrograms/kg/day after discussing benefit
Oral
Once daily
Recheck TFTs after 4 weeks and titrate; postpartum continuation/withdrawal depends on the original diagnosis, dose and TFTs · Calculate weight-based MICROGRAMS, prescribe an achievable tablet-strength schedule, take before breakfast and separate iron/calcium by 4–5 hours
  • The milder subclinical-treatment decision is separate from the clear indication to treat overt hypothyroidism.
Individualised TFT-guided dosing, not a fixed universal maximum
Monitor
  • TSH/FT4 after initiation and every 4–6 weeks during titration; reassess adherence and absorption before increasing
Contraindications / cautions
  • Do not treat isolated low FT4 with normal TSH routinely; untreated adrenal insufficiency or cardiac disease requires specialist review
Pregnancy safety
Essential replacement when indicated; dose follows pregnancy TFTs
Lactation
Continue indicated maternal replacement
RCOG · 2025; May 2026 correction checkedcheckedIN REVIEW