Does Conversol (Liver-Support Supplement) Interfere with Levothyroxine?
Without knowing the specific ingredients in Conversol, it is impossible to definitively state whether it interferes with levothyroxine absorption, but liver-support supplements commonly contain ingredients that are known to interfere with levothyroxine—you should separate Conversol from levothyroxine by at least 4 hours and monitor TSH levels 4-8 weeks after starting the supplement.
Understanding the Problem
The critical issue is that many supplements and medications interfere with levothyroxine absorption through several mechanisms:
- Direct chelation/complexing in the gastrointestinal tract
- Alteration of gastric pH affecting dissolution
- Binding to levothyroxine preventing absorption
Common Liver-Support Supplement Ingredients That Interfere
Liver-support supplements typically contain ingredients that are documented to interfere with levothyroxine:
Calcium and Iron
If Conversol contains calcium or iron (common in liver supplements), these directly bind to levothyroxine and significantly reduce absorption 1. Studies demonstrate that calcium carbonate and ferrous sulfate form insoluble complexes with levothyroxine in the intestinal lumen 2, 3.
Fiber and Herbal Components
Many liver supplements contain fiber or herbal ingredients that can interfere with levothyroxine absorption 4, 3.
Antioxidants and Minerals
Supplements containing chromium have been shown to significantly decrease levothyroxine absorption 5.
Clinical Recommendations
Timing Strategy
Administer levothyroxine at least 4 hours before or after Conversol 6, 1. The FDA label explicitly states: "Administer levothyroxine sodium tablets at least 4 hours before or after drugs known to interfere with levothyroxine sodium absorption" 1.
Monitoring Protocol
- Check TSH 4-8 weeks after starting Conversol 6
- Continue monitoring every 4-8 weeks until stable euthyroid indices are documented 6
- If TSH becomes elevated, increase levothyroxine dose accordingly
Optimal Levothyroxine Administration
Take levothyroxine 30-60 minutes before breakfast with water on an empty stomach 6. This maximizes absorption and minimizes interaction potential with any supplements taken later in the day.
Alternative Approach
If separation timing proves difficult for compliance, consider liquid levothyroxine formulations, which have been shown to circumvent absorption issues caused by multiple interfering substances including calcium, iron, and pH-altering agents 7, 8. These formulations can sometimes be taken simultaneously with interfering substances.
Critical Caveat
The specific ingredients in Conversol matter immensely. Request the complete ingredient list from the patient or manufacturer. If it contains calcium, iron, fiber, chromium, or pH-altering substances, interference is highly likely. Even without these specific ingredients, the prudent approach is to separate administration times given the unpredictable nature of supplement formulations 2, 4.
Bottom Line Algorithm
- Separate dosing by 4+ hours (levothyroxine first, Conversol later)
- Check TSH in 4-8 weeks
- If TSH elevated: increase levothyroxine dose by 12.5-25 mcg increments 6
- If compliance issues: consider liquid levothyroxine formulation 7, 8
- Recheck TSH 4-8 weeks after any dose adjustment until stable 6
The guideline is clear: levothyroxine "should not be taken with substances or medications that interfere with its absorption" 6, and the safest approach with any supplement of uncertain composition is temporal separation and vigilant monitoring.