Levothyroxine and Lopinavir: Interaction Details
AI-assisted, pharmacist-reviewed · Source data updated Aug 8, 2026 · Sources: FDA labeling, DDInter 2.0, cited literature
Levothyroxine
Lopinavir
No brand names on record
How we grade severity & evidence
Severity levels
- Contraindicated: These should generally not be used together.
- Major: Potentially serious — often needs a change or close monitoring.
- Moderate: Can be significant — usually manageable with monitoring.
- Minor: Usually limited clinical impact.
Evidence grades
- Established: Well documented — supported by controlled studies or strong clinical data.
- Probable: Good supporting evidence, though not definitively proven.
- Suspected: Some evidence suggests this interaction, but it is not well established.
- Possible: Limited or conflicting evidence; the interaction may occur.
- Theoretical: Predicted from the drugs' pharmacology; not yet confirmed in people.
Ratings come from the documented interaction literature and are reviewed by a pharmacist. They describe the documented risk of the combination, not what will necessarily happen to you — your dose, timing, and health picture all matter.
What happens
Loss of levothyroxine efficacy
Interaction Deep Dive
A patient experienced persistent hypothyroidism while on lopinavir/ritonavir and levothyroxine. TSH and T4 normalized when lopinavir/ritonavir was discontinued. However, TSH increased and T4 decreased when the lopinavir/ritonavir was re-initiated. Lopinavir/ritonavir was once again discontinued and the TSH and T4 normalized. Levothyroxine undergoes conjugation with glucuronic and sulfuric acids, and lopinavir/ritonavir may have induced glucuronyl transferases resulting in increased conjugation of levothyroxine1.
Why it happens (mechanism)
Unknown
Literature reports
1 report — tap to read
a) An HIV-positive female on lopinavir/ritonavir experienced persistent hypothyroidism despite increasing doses of levothyroxine. Approximately 2 years after starting lopinavir/ritonavir, zidovudine, and lamivudine she required a total thyroidectomy followed by radioiodine therapy for thyroid papillary carcinoma. Levothyroxine was started. Despite increases in levothyroxine dose to 225 mcg/day and addition of liothyronine, the TSH remained elevated at 47.5 mU/L; T4 remained low at 8.5 pmol/L (T3, 3.2 pmol/L); and she was symptomatic. Normal values were 0.2 to 5.1 mU/L for TSH, 11 to 24 pmol/L for serum free T4, and 2.5 to 7 pmol/L for serum free T3. Within 2 months after discontinuation of lopinavir/ritonavir, TSH, T4, and T3 normalized . A rechallenge with lopinavir/ritonavir 9 months later resulted in elevated TSH (18.1 mU/L to 42.9 mU/L) and reduced T4 (8.5 pmol/L to 10.6 pmol/L). Within 3 months of discontinuation of lopinavir/ritonavir and initiation of 3 nucleoside reverse transcriptase inhibitors, the TSH and T4 normalized 1.
Common questions
Can I take Levothyroxine and Lopinavir together?
Loss of levothyroxine efficacy Always confirm with your pharmacist or prescriber before making any change.
How serious is the Levothyroxine and Lopinavir interaction?
It is rated moderate. Can be significant — usually manageable with monitoring.
How quickly could this interaction happen?
The documented onset is "unspecified". The timing of this interaction is not well characterized.
How strong is the evidence for this interaction?
The evidence is graded "probable". Good supporting evidence, though not definitively proven.
From our Q&A
Real reader questions about these medications, each personally answered by our pharmacist:
Questions for your pharmacist
- Does my dose of Levothyroxine or Lopinavir need adjusting while I take them together?
- What symptoms should prompt me to call you or my prescriber right away?
- Does the timing of my doses matter for this combination?
- Is there anything you'd monitor while I'm on both?
References (1)
- Touzot M, Beller CL, Touzot F, et al: Dramatic interaction between levothyroxine and lopinavir/ritonavir in a HIV-infected patient. AIDS 2006; 20(8):1210-1212. PubMed
Keep reading about Levothyroxine
Keep reading about Lopinavir
These medications also interact with supplements
Prescription drugs aren't the whole picture — herbal and dietary supplements can interact with them too. From the evidence-graded Natural Medicines database:
major · moderate · minor — check everything you take with our drug–supplement interaction checker.
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