Ashwagandha and Thyroid Medication: What to Know Before Combining Them
Ashwagandha has become one of the most popular herbs in the country, mostly for stress and sleep. It is also one of the herbs I get the most careful questions about, because it can nudge thyroid hormones — and a lot of people who want help with stress and sleep are also taking thyroid medication. Here is what the research shows and the questions to bring to your provider.
What it is
Ashwagandha is a small shrub in the nightshade family, used in Ayurvedic tradition for centuries as a rasayana — a tonic for resilience. Its active compounds are withanolides. The best-studied extract is a standardized root extract called KSM-66®, which is what we use. Ashwagandha is classed as an adaptogen: in trials it tends to lower cortisol and reduce self-reported stress rather than sedate.
What the research has looked at
- Several randomized trials of 300–600 mg of KSM-66® daily for 8 weeks reported lower perceived stress scores and lower morning cortisol compared with placebo.
- A trial of 600 mg daily for 10 weeks in adults with sleep complaints reported faster time to fall asleep and better sleep quality.
- A small 8-week trial in adults with subclinical hypothyroidism used 600 mg daily and reported increases in T3 and T4 and a fall in TSH — the finding that makes the thyroid question important.
- Trials in healthy adults have also reported modest improvements in strength, recovery, and testosterone in men.
Doses used in research
Most human trials used 300–600 mg per day of a standardized root extract, taken for at least 8 weeks. Our formulas use 600 mg of KSM-66® in the evening, where its calming and cortisol effects fit best.
Interactions and cautions
Because ashwagandha can raise thyroid hormone levels, anyone taking levothyroxine or other thyroid medication — and anyone with hyperthyroidism or Graves' disease — should not start it without their prescriber's approval and a plan to recheck TSH. It can add to the effect of sedatives, sleep medication, and alcohol. Rare cases of liver injury have been reported; stop and call your provider if you notice dark urine, yellowing of the skin or eyes, or pain under the right ribs. It may stimulate the immune system, which matters for people on immunosuppressants or with autoimmune conditions, including MS on disease-modifying therapy.
| Drug / condition | Severity | Why | What to do |
|---|---|---|---|
| Thyroid hormone (levothyroxine) / hyperthyroidism | MODERATE | Raises T3/T4; can push toward hyperthyroid or reduce need for medication | Monitor TSH; avoid in Graves/hyperthyroidism |
| Sedatives, benzodiazepines, barbiturates, alcohol | MODERATE | Additive CNS depression / GABA-ergic | Avoid combining; no driving after evening dose |
| Immunosuppressants | MODERATE | Immunostimulant | Consult prescriber; caution in autoimmune disease incl. MS on DMTs |
| Antihypertensives | MINOR | Mild BP lowering | Monitor |
| Antidiabetic drugs | MINOR | Mild glucose lowering | Monitor |
| Hepatotoxic drugs / liver disease | MODERATE | Rare case reports of drug-induced liver injury | Discontinue if jaundice, dark urine, RUQ pain |
| Pregnancy | MAJOR | Possible abortifacient (traditional use) | Contraindicated |
Where we use it
Ashwagandha KSM-66® 600 mg is in Mitochondrial Protect (bedtime), Metabolic Boost PM (afternoon), and Evening Calm & Sleep (300 mg). If you take a thyroid medication, please review the full ingredient list of any of these with your provider before starting.