Raloxifene and Levothyroxine: Interaction Details
AI-assisted, pharmacist-reviewed · Source data updated Aug 8, 2026 · Sources: FDA labeling, DDInter 2.0, cited literature
Levothyroxine
Raloxifene
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
Decreased levothyroxine efficacy
Interaction Deep Dive
Coadministration of levothyroxine and raloxifene may decrease levothyroxine absorption34. Avoid concomitant use if possible. If coadministration is required, administer levothyroxine at least 12 hours before raloxifene 1. Monitor closely during coadministration and adjust levothyroxine dose if necessary 2.
Why it happens (mechanism)
Reduced absorption of levothyroxine
Literature reports
2 reports — tap to read
a) Decreased absorption of levothyroxine when coadministered with raloxifene was described in a case report. A 47-year-old woman with a history of primary hypothyroidism stable on levothyroxine 0.05 mg/day began treatment with raloxifene 60 mg/day and administered both drugs together 1 hour before breakfast every morning. She had no other significant medical history. Other medications included a multivitamin and calcium supplement (administered at least 4 hours after the other drugs). Ten months after initiating raloxifene, clinical symptoms of hypothyroidism occurred and TSH was found to be 4.62 micro-international units/mL. One month after increasing levothyroxine to 0.075 mg, TSH was within normal limits. Over 1 year later, clinical hypothyroidism symptoms were present again, and TSH was found to be 4.64 micro-international units/mL. Four months after increasing levothyroxine to 0.088 mg, TSH was still elevated at 5.14 micro-international units/mL. Subsequently, the levothyroxine dosage was increased again to 0.1 mg every morning. At this point, a drug interaction causing levothyroxine malabsorption was suspected and the patient was advised to separate raloxifene and levothyroxine administration by 12 hours. Three months later, hyperthyroidism occurred (TSH, 0.17 micro-international units/mL) and levothyroxine was decreased slightly. After another 3 months, hyperthyroidism was still present (TSH, 0.06 micro-international units/mL) and levothyroxine was decreased again to 0.088 mg. Following this decrease, and with continued administration of levothyroxine alone in the morning, TSH was within normal limits over the next year. Of note, the same levothyroxine brand was dispensed each time for this patient and she was adherent with her medication regimen 3.
b) A case has been described of a 79-year-old female patient in whom raloxifene caused malabsorption of levothyroxine. The patient had a subtotal thyroidectomy in 1970. With daily levothyroxine supplementation, her TSH levels remained normal for several years. She was prescribed raloxifene for osteopenia. Within 2 to 3 months, an elevated TSH level of 14.5 microunits/mL and symptoms of hypothyroidism led to an increase in levothyroxine sodium dosage from 0.15 mg to 0.2 mg/day. Over the next several months levothyroxine sodium was increased to 0.3 mg/day. Nine months after starting raloxifene she presented with a TSH of 9.36 microunits/mL. On 2 occasions separated by 4 weeks, T4 levels were obtained at 0, 30, 60, 90, 120, 180, 240, 300, and 360 minutes after ingestion of 1 mg levothyroxine sodium with and without the coadministration of 60 mg of raloxifene. Compared with levothyroxine alone, the results demonstrated lower levels of T4 at all study points following combined administration of levothyroxine and raloxifene 4.
Common questions
Can I take Raloxifene and Levothyroxine together?
Decreased levothyroxine efficacy Always confirm with your pharmacist or prescriber before making any change.
How serious is the Raloxifene and Levothyroxine interaction?
It is rated moderate. Can be significant — usually manageable with monitoring.
How quickly could this interaction happen?
The documented onset is "delayed". Effects tend to build up gradually over days to weeks.
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 Raloxifene or Levothyroxine 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 (4)
- Centanni M, Duntas L, Feldt-Rasmussen U, et al: ETA guidelines for the use of levothyroxine sodium preparations in monotherapy to optimize the treatment of hypothyroidism. Eur Thyroid J 2025; 14(4):e250123. PubMed
- Liu H, Lu M, Hu J, et al: Medications and food interfering with the bioavailability of levothyroxine: a systematic review. Ther Clin Risk Manag 2023; 19:503-523. DOI
- Garwood CL, Van Schepen KA, McDonough RP, et al: Increased thyroid-stimulating hormone levels associated with concomitant administration of levothyroxine and raloxifene. Pharmacotherapy 2006; 26(6):881-885. PubMed
- Siraj E, Gupta M, & Reddy S: Raloxifene causing malabsorption of levothyroxine. Arch Intern Med 2003; 163:1367-1370. DOI
Keep reading about Levothyroxine
Keep reading about Raloxifene
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