Effect of Rifampin on Thyroid Function Test in Patients on Levothyroxine Medication

Nothing to add - except to ask if anyone has ever had Rifampicin? And did they notice anything from taking it?

(Rifampin is another name for rifampicin which is an antibiotic.)

PLoS One. 2017 Jan 12;12(1):e0169775. doi: 10.1371/journal.pone.0169775. eCollection 2017.

Effect of Rifampin on Thyroid Function Test in Patients on Levothyroxine Medication.

Kim HI1, Kim TH1, Kim H1, Kim YN1, Jang HW2, Chung JH1, Moon SM3, Jhun BW3, Lee H3, Koh WJ3, Kim SW1.

Author information

1Division of Endocrinology & Metabolism, Department of Medicine, Thyroid Center, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, South Korea.

2Department of Medical Education, Sungkyunkwan University School of Medicine, Seoul, South Korea.

3Division of Pulmonary and Critical Care Medicine, Department of Medicine, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, South Korea.



Levothyroxine (LT4) and rifampin (RIF) are sometimes used together; however, no clinical studies have assessed the effects of these drugs on thyroid function or the need to adjust LT4 dose.


We retrospectively reviewed the records of 71 Korean patients who started RIF during LT4 treatment. Clinically relevant cases that required dose adjustment according to the American Thyroid Association (ATA)/American Association of Clinical Endocrinologists (AACE) guidelines were identified, and risk factors of increased LT4 dose were analyzed.


After administering RIF, median serum thyroid-stimulating hormone (TSH) level (2.58 mIU/L, interquartile range [IQR] 0.21-7.44) was significantly higher than that before RIF (0.25 mIU/L, IQR, 0.03-2.62; P < 0.001). An increased LT4 dose was required for 50% of patients in the TSH suppression group for thyroid cancer and 26% of patients in the replacement group for hypothyroidism. Risk factor analysis showed that remaining thyroid gland (odds ratio [OR] 9.207, P = 0.002), the time interval between starting RIF and TSH measurement (OR 1.043, P = 0.019), and baseline LT4 dose per kg body weight (OR 0.364, P = 0.011) were clinically relevant variables.


In patients receiving LT4, serum thyroid function test should be performed after starting RIF treatment. For patients with no remnant thyroid gland and those receiving a lower LT4 dose, close observation is needed when starting RIF and TB medication.

PMID: 28081173

DOI: 10.1371/journal.pone.0169775


Full paper freely available here:


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12 Replies

  • Quite a few years ago I had a discussion with my GP about possibly prescribing rifampicin, but he checked and said it was not available in the UK. That may have changed since then of course.

  • I checked! It is listed in British National Formulary - now. :-) Didn't read it very closely. :-(

  • Gingerbread - I took Rifampacin over 43 years ago in the UK - along with other nasty stuff :-(

  • You know after I had posted that, I had a feeling something wasn't right. I've since realised the one I discussed with my GP was rifaximin. Thanks for putting me right Marz :)

  • Which has this paper:

    J Clin Endocrinol Metab. 2007 Nov;92(11):4180-4. Epub 2007 Aug 14.

    Association between hypothyroidism and small intestinal bacterial overgrowth.

    Lauritano EC1, Bilotta AL, Gabrielli M, Scarpellini E, Lupascu A, Laginestra A, Novi M, Sottili S, Serricchio M, Cammarota G, Gasbarrini G, Pontecorvi A, Gasbarrini A.

    Author information

    1Internal Medicine Department, Catholic University of Sacred Heart, Gemelli Hospital, Largo A. Gemelli, 8, 00168 Rome, Italy.



    Small intestinal bacterial overgrowth is defined as an abnormally high bacterial population level in the small intestine. Intestinal motor dysfunction associated with hypothyroidism could predispose to bacterial overgrowth. Luminal bacteria could modulate gastrointestinal symptoms and interfere with levothyroxine absorption. The aims of the present study were to assess the prevalence and clinical pattern of bacterial overgrowth in patients with a history of overt hypothyroidism and the effects of bacterial overgrowth decontamination on thyroid hormone levels.


    A total of 50 consecutive patients with a history of overt hypothyroidism due to autoimmune thyroiditis was enrolled. Diagnosis of bacterial overgrowth was based on positivity to a hydrogen glucose breath test. Bacterial overgrowth positive patients were treated with 1,200 mg rifaximin each day for a week. A glucose breath test, gastrointestinal symptoms, and thyroid hormone plasma levels were reassessed 1 month after treatment.


    A total of 27 patients with a history of hypothyroidism demonstrated a positive result to the breath test (27 of 50, 54%), compared with two in the control group (two of 40, 5%). The difference was statistically significant (P < 0.001). Abdominal discomfort, flatulence, and bloating were significantly more prevalent in the bacterial overgrowth positive group. These symptoms significantly improved after antibiotic decontamination. Thyroid hormone plasma levels were not significantly affected by successful bacterial overgrowth decontamination.


    The history of overt hypothyroidism is associated with bacterial overgrowth development. Excess bacteria could influence clinical gastrointestinal manifestations. Bacterial overgrowth decontamination is associated with improved gastrointestinal symptoms. However, fermenting carbohydrate luminal bacteria do not interfere with thyroid hormone levels.

    PMID: 17698907

    DOI: 10.1210/jc.2007-0606


  • I was given Rifampicin in an NHS hospital in 2014. It is normally used for the treatment of epilepsy as it affects the electrical impulses in the brain. I was given it to treat septic shock. It also gave me hallucinations.

  • It was part of the treatment I had for ileo-caecal TB ....

  • Is it one of the antibiotics that causes, let's call it "digestive distress"? Let's face it, many antibiotics have that effect... :)

    So could it be as simple as antibiotics reduce absorbency of levothyroxine?

  • It could - but I don't recall it being regarded as a universal effect.

    Indeed, bizarrely, I find this, which seems to tell the opposite story:

    Thyroid. 2013 Nov;23(11):1374-8. doi: 10.1089/thy.2013.0014. Epub 2013 Oct 16.

    Ciprofloxacin and rifampin have opposite effects on levothyroxine absorption.

    Goldberg AS1, Tirona RG, Asher LJ, Kim RB, Van Uum SH.

    Author information

    11 Division of Endocrinology and Metabolism, Department of Medicine, Schulich School of Medicine and Dentistry, Western University , London, Canada .



    Levothyroxine (L-T4) absorption varies between individuals, and can be affected by various concomitantly administered drugs. Case reports have indicated an association between cotreatment with ciprofloxacin or rifampin and hypothyroidism in patients on a stable L-T4 dose.


    The effects of two antibiotics on T4 absorption were prospectively assessed in a double-blind, randomized, crossover fashion. Eight healthy volunteers received 1000 μg L-T4 combined with placebo, ciprofloxacin 750 mg, or rifampin 600 mg as single doses. We measured total plasma thyroxine (T4) concentrations over a 6-hour period after dosing using liquid chromatography-tandem mass spectrometry. For each study arm, areas under the T4 plasma concentration-time curve (T4 AUCs) were compared.


    Coadministration of ciprofloxacin significantly decreased the T4 AUC by 39% (p = 0.035), while, surprisingly, rifampin significantly increased T4 AUC by 25% (p = 0.003).


    Intestinal absorption of L-T4 is differentially affected by acute coadministration of ciprofloxacin or rifampin. Mechanistic studies focused on intestinal and possibly hepatic thyroid hormone transporters are required to explain the observed drug interactions with L-T4.

    PMID: 23647409

    DOI: 10.1089/thy.2013.0014


  • Hmm. :) Oh well, just a guess - a wrong one, apparently.

  • Jazzw, According to wiki:

    Common side effects include nausea, vomiting, diarrhea, and loss of appetite. It often turns urine, sweat, and tears a red or orange color. Liver problems or allergic reactions may occur. en.wikipedia.org/wiki/Rifam...

    Which does not sound very nice and yes, sure potential there for reduced absorption of levo :(

  • I was on rifampicin for a month recently. I increased my T4 dose during the course and didn't feel much different. My free T3 and T4 have been on the low side.

    My doctor has me taking 200 billion CFU of probiotics and it still did a number on my digestion.

    Rifampicin is noted for turning your pee orange. It's also important to monitor liver function.

    I'd be far more concerned about severe permanent side effects from Cipro and other fluoroquinones, though. Must logically think through risks and benefits before taking any antibiotics.

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