Weight-Based Levothyroxine Dose Calculator
Estimates the starting levothyroxine dose for primary hypothyroidism (NICE NG145). Adults under 65 without cardiovascular disease: 1.6 micrograms/kg/day, rounded to the nearest 25 micrograms. Adults aged 65 and over or with cardiovascular disease: start 25–50 micrograms/day and titrate. Children: use a children's formulary.
Score interpretation
Adults < 65 without cardiovascular disease: full replacement 1.6 µg/kg/day rounded to 25 µg. Adults ≥ 65 or with cardiovascular disease: starting dose 25 µg/day (25–50 µg) — titrate. Children: use a children's formulary.
→ Titrate to TSH and symptoms per NICE NG145.
Interpretation bands for the Levothyroxine Dose. Apply clinical judgement and local guidance.
References
- NICE NG145. Thyroid disease: assessment and management. National Institute for Health and Care Excellence; 2019.
- Jonklaas J et al. Guidelines for the Treatment of Hypothyroidism: Prepared by the American Thyroid Association Task Force. Thyroid. 2014;24(12):1670–1751.
Related
Curated clinical cross-links plus same-class fallbacks.
- Levothyroxine · Thyroid Hormone
- Levothyroxine sodium · Thyroid hormone (T4)
- Levothyroxine (Elderly) · Thyroid Hormone
- Enoxaparin (VTE in Pregnancy) · Low Molecular Weight Heparin (LMWH) — VTE Prophylaxis/Treatment
- Low Molecular Weight Heparin (Pregnancy VTE) · Anticoagulant — VTE Treatment and Prophylaxis in Pregnancy
- Dalteparin · Low Molecular Weight Heparin — VTE Treatment / Cancer-Associated Thrombosis
- Diabetic Ketoacidosis (DKA) · JBDS 2013 / Joint British Diabetes Societies; NICE NG17
- Adult Hypoglycaemia (Treated Diabetes) · JBDS-IP (2023): Hospital Management of Hypoglycaemia
- Adrenal Crisis · Society for Endocrinology Emergency Guidance (2024)
- Type 2 Diabetes Management · NICE NG28 2022
- Hyperthyroidism Management · BTA / ETA 2018
- Adrenal Insufficiency · Society of Endocrinology / ESE 2016
Decision support only — verify against a current formulary, NICE, or your local guideline before clinical use.