Shilajit and Levothyroxine (L‑Thyroxine, Euthyrox, L‑Thyroxin Henning)
Leila WehrhahnUpdated:Key points at a glance:
Shilajit may influence the absorption of levothyroxine. This is thought to be linked to minerals such as calcium and iron, which can form complexes. Animal data also suggest potential effects of fulvic and humic acids. Levothyroxine is usually taken in the morning on an empty stomach with water. It is often recommended to leave at least a 4‑hour interval between taking levothyroxine and shilajit. Thyroid-stimulating hormone (TSH) levels are commonly checked 6 to 8 weeks after starting or stopping supplements such as shilajit. It is advisable to choose products that have been tested for quality, including possible heavy metal content. Direct clinical studies on this specific interaction are currently lacking.
Shilajit is a traditional natural substance composed of humus-like materials (primarily fulvic and humic acids) with varying amounts of minerals and trace elements. Levothyroxine (brand names include Euthyrox, L‑Thyroxin, L‑Thyroxin Henning) is a medicine with a narrow therapeutic range. If Shilajit is taken close in time to levothyroxine, this may interfere with the absorption and effect of levothyroxine, potentially leading to under‑ or over‑replacement effects. (1)(5).
You can find more information about the properties of Shilajit in our article Shilajit effects.
Shilajit may interfere with levothyroxine absorption. Take levothyroxine strictly separately from Shilajit.
How does the interaction occur?
1) Mineral-related complex formation in the gut
Many Shilajit products contain relevant amounts of minerals such as calcium, magnesium and potassium as well as various trace elements. Minerals – especially calcium and iron – can form poorly soluble complexes with levothyroxine in the gastrointestinal tract. This can reduce the absorption of levothyroxine. For calcium, this effect has been shown in human studies, with levothyroxine absorption reduced by around 20–25%. (2)(5).
2) Effects of fulvic/humic acids on the thyroid axis (animal data)
Fulvic and humic acids – the main components of Shilajit – altered TSH and the T4/T3 ratio in rat studies, suggesting a potential influence on thyroid regulation. Clinical data in humans are not yet available, so this mechanism remains theoretical, although considered biologically plausible. (4).
3) Narrow therapeutic range of levothyroxine
Even small fluctuations in levothyroxine absorption can noticeably affect TSH and related symptoms. Guidelines advise taking the medicine on an empty stomach and keeping a clear time interval from mineral-containing supplements. (1)(3).
Clinical evidence
There are currently no direct studies on the combined use of Shilajit and levothyroxine. The assessment is based on three elements: (a) the well-documented interaction between levothyroxine and minerals (especially calcium/iron), (b) the known variability of levothyroxine absorption, and (c) animal data on fulvic/humic acids. A crossover study in healthy volunteers showed that concurrent administration of calcium carbonate, citrate or acetate significantly reduced levothyroxine absorption; professional societies therefore recommend time intervals between intake. (1)(2).
Reviews and analytical studies on the composition and purity of Shilajit describe considerable differences between products. (5).
Risk assessment
Severity
Moderate to relevant. When taken at the same time, under‑replacement effects (such as tiredness, weight gain, sensitivity to cold) may occur; conversely, suddenly stopping Shilajit in someone whose levothyroxine dose has been adjusted while using it could theoretically contribute to relative over‑replacement (for example palpitations, nervousness). (1)(3).
Likelihood
Likely if Shilajit is taken at the same time as, or shortly before or after, levothyroxine, particularly with calcium‑ or mineral‑rich products. If intake times are kept clearly separate, the risk appears to decrease significantly. (1)(2).
Product safety
In addition to potential interactions, there is a general safety consideration: some ayurvedic products (including Shilajit preparations) may be contaminated with heavy metals. Official bodies have issued warnings about untested products. It is advisable to choose purified, laboratory‑tested Shilajit products with available test reports. (6).
Further information: Shilajit interactions and Shilajit side effects.
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Taking both at the same time increases the risk of interaction; be aware of quality differences and potential heavy metal contamination.
Shilajit Capsules
Practical recommendations
Timing and spacing of intake
- Take levothyroxine in the morning on an empty stomach with water. Wait 30–60 minutes before eating breakfast.
- Interval to Shilajit: allow at least 4 hours before or after levothyroxine. It may be practical to plan Shilajit at lunchtime or in the evening with a meal. (1)(3).
Example daily schedule
| Time | Measure |
|---|---|
| 07:00 | Levothyroxine with water (on an empty stomach), then do not eat for 30–60 minutes |
| 12:00–14:00 | Shilajit with a meal |
| Evening | Other supplements (calcium/iron) – still >4 hours apart from levothyroxine |
Monitoring and dose adjustment
Starting or stopping Shilajit? Have TSH (and fT4 where appropriate) checked after about 6–8 weeks and discuss with your doctor whether a levothyroxine dose adjustment is needed. If your thyroid levels are already stable, later routine checks may be sufficient. (3).
Formulations to consider
If absorption problems persist (for example due to multiple medicines or gastrointestinal issues), alternative levothyroxine formulations (liquid or softgel) can be considered according to European recommendations; discuss this with your doctor. (1).
Choice of product
Choose purified, certified Shilajit with up-to-date laboratory analysis (heavy metals, microbiology). Buy only from trustworthy suppliers and avoid products without evidence of quality control. (6).
Take levothyroxine in the morning on an empty stomach; take Shilajit only 4+ hours later. After starting or stopping Shilajit, have TSH checked after 6–8 weeks.
Medical disclaimer
Important notice: This information does not replace professional medical advice. Always consult your doctor or pharmacist before taking Shilajit together with levothyroxine. Every individual may respond differently to food supplements and medicines.