Can I Take Ashwagandha with Low-Dose Naltrexone?

Naltrexone is an opioid receptor antagonist approved by the FDA at 50 mg for opioid and alcohol use disorder. Low-dose naltrexone (LDN) refers to the same molecule compounded at 1.5 to 4.5 mg, an off-label practice not itself FDA-reviewed as a dosage form. Ashwagandha (Withania somnifera) is an Ayurvedic herbal supplement, most often studied as the proprietary extracts KSM-66 or Sensoril, standardized to withanolide content. Naltrexone is a prescription drug; ashwagandha is an unregulated dietary supplement, and the two are not chemically related.

No published pharmacokinetic study has shown that ashwagandha changes naltrexone blood levels. The realistic concern is pharmacodynamic: ashwagandha lowers cortisol and raises thyroid hormone levels in randomized trials, and both changes can shift the immune and endocrine environment that LDN is being used to modulate. That means the combination is not a blanket safety question but a subgroup question, the people who need labs before combining are those on thyroid replacement, those with adrenal insufficiency, and those with androgen-sensitive autoimmune disease, not the general LDN user.

What LDN Is Thought to Do

The most cited mechanistic explanation, from Younger, Parkitny, and McLain's 2014 review, proposes that low-dose naltrexone acts on microglial Toll-like receptor 4 (TLR4) in addition to classic opioid receptor blockade, and that transient nightly blockade triggers a rebound rise in endogenous opioids (beta-endorphin, met-enkephalin) that may reduce pro-inflammatory cytokines such as IL-6 and TNF-alpha (Younger 2014). This is a proposed mechanism from a narrative review, not a settled pharmacologic fact confirmed across large trials. LDN is prescribed off-label for fibromyalgia, Crohn's disease, multiple sclerosis, and other conditions where clinicians believe low-grade neuroinflammation plays a role. People managing these conditions frequently look for anti-inflammatory supplements, which is the practical reason ashwagandha comes up so often alongside LDN.

What Ashwagandha Does, By the Numbers That Exist

Cortisol

A 2012 double-blind RCT (N=64) found that 300 mg of KSM-66 extract twice daily reduced serum cortisol by 27.9% versus 7.9% with placebo over 60 days (P<0.001) (Chandrasekhar 2012). A separate review of ashwagandha anxiety trials corroborates a consistent cortisol-lowering signal across studies of similar design (Pratte 2014). Cortisol is itself an immune regulator, so a meaningful and sustained drop is mechanistically relevant to anyone using LDN for an immune-mediated condition, even though no trial has tested the two together.

Testosterone

A trial in men with fertility concerns reported that 5 g/day of ashwagandha root powder raised serum testosterone by roughly 17% from baseline after 90 days (Mahdi 2011); a separate 8-week resistance-training trial found a smaller but comparable rise with 300 mg KSM-66 twice daily (Wankhede 2015). These populations (infertile men, resistance-trained men) do not represent LDN users directly, so the testosterone finding should be read as a plausible signal to watch in androgen-sensitive autoimmune disease, not a number that transfers cleanly to that population.

Thyroid Hormones

A randomized trial in patients with subclinical hypothyroidism found that 600 mg/day of ashwagandha root extract for 8 weeks raised T3 and T4 measurably above placebo (Sharma 2018). This is the single most clinically actionable finding for LDN patients who are also on levothyroxine or desiccated thyroid, because a supplement-driven hormone rise on top of a stable prescription dose can push a patient above their therapeutic target without any change in their medication.

Is This a Liver Interaction or a Signaling Interaction?

Pharmacokinetics. Naltrexone is metabolized mainly by carbonyl reductase to 6-beta-naltrexol, not primarily through cytochrome P450 pathways (Verebey 1976). Ashwagandha withanolides show mild CYP3A4 inhibition in laboratory studies, but no published trial has measured naltrexone blood levels with and without concurrent ashwagandha. The absence of a documented interaction is not proof that none exists at higher supplement doses; it means the risk, based on available mechanism and dose data, appears low.

Pharmacodynamics. This is where the real overlap sits. Ashwagandha has shown anti-inflammatory activity in small human and animal studies, including reduced high-sensitivity CRP in an 18-patient trial after four weeks of Sensoril (Agnihotri 2013). Two agents that both dampen inflammatory signaling are not automatically dangerous together; for many fibromyalgia or IBD patients, additive anti-inflammatory effect is exactly what is wanted. The concern narrows to three groups:

1. Patients on thyroid replacement, where ashwagandha's hormone-raising effect can cause functional over-replacement.
2. Patients with androgen-sensitive autoimmune disease, where a modest testosterone rise could shift disease activity in an unpredictable direction.
3. Patients with adrenal insufficiency on physiologic hydrocortisone, where a 20 to 28% cortisol reduction from ashwagandha could push morning cortisol below a functional threshold.

Do LDN and Ashwagandha Need to Be Taken at Different Times?

No dose-separation window is established as necessary, because this is not an absorption or enzyme-competition interaction. LDN is conventionally taken at bedtime; its receptor blockade is transient and clears well before morning. Taking ashwagandha earlier in the day is a matter of routine and mild sedation avoidance rather than a documented pharmacokinetic requirement. A 2019 RCT found that 300 mg of KSM-66 twice daily improved subjective sleep quality versus baseline (Langade 2019), so patients taking both agents at night should expect mild additive drowsiness rather than a dangerous interaction.

Evidence-Status Interaction Assessment

This table distinguishes between interactions supported by existing research and those with a plausible biological basis but lacking clinical validation, allowing healthcare providers to identify the boundary of established evidence for low-dose naltrexone combinations.

What the LDN Trial Evidence Shows for Its Target Conditions

Knowing how strong LDN's own evidence base is helps calibrate how much margin exists for adding a supplement that shifts immune tone.

Fibromyalgia. A small pilot (N=10) found roughly a 30% reduction in symptom scores with LDN 4.5 mg versus placebo (Younger 2009). A follow-up crossover trial (N=31) confirmed a statistically significant pain reduction and found that lower baseline inflammatory markers predicted better response (Younger 2013). That inflammatory-marker link means anything that changes baseline inflammation, ashwagandha included, could theoretically shift a patient's response, though this has not been tested directly.

Crohn's disease. An open-label pediatric pilot (N=40) reported high response and remission rates with LDN 0.1 mg/kg over 8 weeks (Smith 2011). This was open-label and uncontrolled, so the numbers should be read as hypothesis-generating rather than confirmed efficacy.

Multiple sclerosis. A pilot trial (N=80) found LDN 4.5 mg improved mental-health quality-of-life scores over 16 weeks without reducing relapse rate (Cree 2010). No trial has tested ashwagandha alongside LDN in MS.

Safety Considerations Beyond the Interaction Itself

Liver. Case reports have linked ashwagandha to liver injury in a small number of patients, with recovery after discontinuation (Björnsson 2021). LDN at standard doses is not considered hepatotoxic. Patients with pre-existing liver disease should discuss both agents with their prescriber and consider baseline liver enzymes before combining them.

Pregnancy. Neither agent has adequate human safety data in pregnancy. Ashwagandha has traditional use as an abortifacient in Ayurvedic texts and uterine-stimulating activity in animal studies. Ashwagandha is a dietary supplement and has not been evaluated by the FDA as a drug for any indication. Both agents are generally advised to be stopped at conception, and this should be confirmed with an obstetric provider rather than decided from a general article.

A Practical Monitoring Approach

Patients starting ashwagandha while already stable on LDN, or planning to start both together, should get baseline labs relevant to their individual risk group: TSH and free T4 if on thyroid medication or with known thyroid disease, morning cortisol if on adrenal replacement, and a complete metabolic panel if there is any liver history. Repeating TSH and free T4 around 4 weeks captures the timeframe in which ashwagandha's thyroid effect has been observed in trials. Symptom and disease-activity tracking (pain scores, flare frequency, standard disease-activity indices) around 12 weeks helps distinguish a supplement effect from ordinary variation in the underlying condition. If symptoms worsen in that window, pausing ashwagandha for several weeks is a reasonable way to test whether it, rather than the LDN dose, is responsible.

The American Association of Clinical Endocrinologists and American Thyroid Association's joint guideline on hypothyroidism states that serum TSH should be maintained within the normal reference range for most patients treated for hypothyroidism (Garber 2012), which is the standard against which any thyroid-stimulating supplement added to a stable regimen should be checked.

What Clinicians Generally Advise

The LDN Research Trust, a patient advocacy and information organization, advises that patients disclose all concurrent supplements to their LDN prescriber, particularly adaptogens and substances with known immunological activity (LDN Research Trust). This is a general disclosure recommendation rather than a specific ashwagandha ruling, and prescribers should be consulted directly for guidance tailored to an individual patient's labs and diagnosis. A quoted clinical opinion on this specific combination could not be verified against a citable source and has been left out of this draft pending confirmation.

Evidence Boundary

Established: Ashwagandha lowers cortisol and raises thyroid hormones in randomized trials of non-LDN populations. Naltrexone's metabolism does not rely primarily on CYP450 pathways.

Plausible but unproven: That these hormonal effects meaningfully interact with LDN's immune mechanism in a clinically important way for most patients, and that additive anti-inflammatory effects improve outcomes when both are used together.

Not established: Any pharmacokinetic interaction between the two agents, and any clinical outcome data (positive or negative) for concurrent use in fibromyalgia, Crohn's, MS, or other LDN-treated conditions.

Because no trial has enrolled patients using both agents together, decisions about combining them rest on extrapolation from separate evidence bases, not on direct interaction data.