Switching guide
How to switch from levothyroxine to Armour Thyroid
NDT contains T4+T3 ratio from porcine source. Switch sometimes done for persistent symptoms on T4-only despite normal TSH.
Reviewed by ClearHormones Editorial Team · Updated 2026-04-20
Why switch
- Persistent fatigue/brain fog on levothyroxine despite normal labs
- Want T3 component
- Genetic T4-to-T3 conversion impairment suspected
Why not to switch
- Doing well on levothyroxine
- Cardiovascular disease (T3 can spike heart rate)
- Insurance won't cover Armour
Step-by-step
- Confirm switch with endocrinologistNDT not endorsed by ATA guidelines. Specialist support helpful. Get baseline labs: TSH, free T4, free T3.
- Calculate equivalent NDT dose100 mcg levothyroxine ≈ 60 mg Armour. Round to nearest available dose (15, 30, 60, 90, 120 mg).
- Start ArmourTake morning, empty stomach, 30-60 min before food. Same routine as levothyroxine.
- Recheck labs at 6-8 weeksExpect TSH to stabilize at slightly different level. Free T3 will be measurable (on T4-only is suppressed).
- Symptom checkMost patients report energy/mental clarity improvement if switch was right call. If symptoms unchanged, NDT was not the issue.
- Confirm switch with endocrinologist(Week 0)NDT not endorsed by ATA guidelines. Specialist support helpful. Get baseline labs: TSH, free T4, free T3.
- Calculate equivalent NDT dose(Week 0)100 mcg levothyroxine ≈ 60 mg Armour. Round to nearest available dose (15, 30, 60, 90, 120 mg).
- Start Armour(Week 1)Take morning, empty stomach, 30-60 min before food. Same routine as levothyroxine.
- Recheck labs at 6-8 weeks(Week 6-8)Expect TSH to stabilize at slightly different level. Free T3 will be measurable (on T4-only is suppressed).
- Symptom check(Week 8)Most patients report energy/mental clarity improvement if switch was right call. If symptoms unchanged, NDT was not the issue.
⚠ Warnings
- Cardiac symptoms (palpitations, AFib risk)
- Insurance often won't cover
- Lot-to-lot variability higher than synthetic T4
Other switching guides
Not medical advice. Always discuss medication changes with your prescriber. See our editorial methodology.