Can I Take Ashwagandha with Prolia (Denosumab)?

What Is Denosumab (Prolia) and How Does It Work?

Denosumab is a fully human monoclonal antibody that binds RANK ligand (RANKL), blocking osteoclast formation, function, and survival. By suppressing osteoclast activity, it shifts the bone remodeling balance toward net bone gain.

The FDA approved Prolia in June 2010 for postmenopausal women with osteoporosis at high fracture risk [1]. A single 60 mg subcutaneous dose every 6 months reduces bone resorption markers (serum CTX) by roughly 86% within 1 month [2]. In the key FREEDOM trial (N=7,868), denosumab reduced new vertebral fracture risk by 68%, hip fracture risk by 40%, and nonvertebral fracture risk by 20% versus placebo over 36 months [2].

Mechanism: RANKL Inhibition

Osteoclasts depend on the RANK/RANKL/OPG axis for maturation. Denosumab mimics osteoprotegerin (OPG) by binding RANKL with high affinity, preventing it from activating RANK on osteoclast precursors. The result is a rapid, reversible suppression of bone resorption.

Pharmacokinetics Relevant to Supplement Interactions

Denosumab is not metabolized by cytochrome P450 enzymes. It is cleared through the reticuloendothelial system via catabolism to small peptides and amino acids, the same pathway used for endogenous immunoglobulins [3]. This fact is central to understanding why classical pharmacokinetic supplement interactions (CYP induction, P-glycoprotein competition) do not apply here.

What Is Ashwagandha and What Does It Do Physiologically?

Ashwagandha (Withania somnifera) is an adaptogenic herb used in Ayurvedic medicine for stress, energy, and cognitive support. Its active compounds include withanolides, alkaloids, and saponins.

In clinical trials, standardized root extract at 300 to 600 mg/day produces measurable hormonal shifts: a 14 to 32% reduction in serum cortisol [4], a modest increase in testosterone in men (mean increase roughly 14.7% in one 8-week RCT) [5], and, in some patients, a significant rise in serum T3 and T4 levels.

Cortisol Reduction and Bone

Chronic glucocorticoid excess is a recognized driver of secondary osteoporosis. The AACE/ACE 2020 guidelines on glucocorticoid-induced osteoporosis identify cortisol-mediated suppression of osteoblast differentiation as a primary mechanism of bone loss [6]. If ashwagandha reduces endogenous cortisol, in theory this could support osteoblast function. That directional effect would be additive to, not antagonistic of, denosumab's anti-resorptive effect.

The practical caveat: the cortisol reductions seen in ashwagandha trials are modest (roughly 11 to 32 nmol/L in absolute terms) and affect endogenous cortisol at physiological levels, not pharmacological glucocorticoid dosing. The clinical bone-density consequence of this cortisol shift has not been studied directly.

Testosterone Effects and Bone Remodeling

Testosterone supports bone formation through androgen receptors on osteoblasts and through peripheral aromatization to estradiol. In postmenopausal women (the primary Prolia population), baseline testosterone is already low. A modest ashwagandha-driven androgen increase may theoretically support bone density, not diminish it.

One 8-week, double-blind RCT (N=57 male subjects) found that KSM-66 ashwagandha extract at 300 mg twice daily raised serum testosterone from a mean of 530 ng/dL to 607 ng/dL (P<0.05) [5]. Whether similar androgen changes occur in postmenopausal women using ashwagandha is not established in the published literature.

Thyroid Hormone Effects: The More Clinically Relevant Concern

Ashwagandha increases thyroid hormone levels in some patients. A prospective study published in the Journal of Alternative and Complementary Medicine (N=50) showed that 600 mg/day of ashwagandha root extract for 8 weeks produced statistically significant increases in serum T3 (mean increase 41.5 ng/dL) and T4 (mean increase 19.6 ng/dL) with a reduction in TSH, compared to placebo [7].

Hyperthyroidism accelerates bone turnover. The American Thyroid Association notes that overt hyperthyroidism increases fracture risk and raises bone resorption markers [8]. If a patient on Prolia develops subclinical or overt hyperthyroidism partly driven by ashwagandha supplementation, the anti-resorptive benefit of denosumab could be partially offset.

This is the most clinically meaningful pharmacodynamic concern in this supplement-drug pairing.

Is the Ashwagandha-Denosumab Interaction Pharmacokinetic or Pharmacodynamic?

The interaction is exclusively pharmacodynamic. No pharmacokinetic interaction pathway exists because denosumab bypasses hepatic CYP metabolism entirely [3].

Pharmacokinetic Pathway: Not Applicable

Ashwagandha withanolides are metabolized partly through CYP3A4 and CYP2D6. Denosumab does not use these enzymes. No competition for protein binding, renal clearance, or hepatic first-pass metabolism exists between these two agents. Dose-separation timing (the "take 2 hours apart" advice common with some supplement-drug pairings) does not apply here.

Pharmacodynamic Pathways: What to Watch

Three hormonal axes are theoretically relevant:

1. Cortisol axis. Ashwagandha reduces cortisol; high cortisol impairs osteoblasts. The effect direction is not harmful to bone health, but unmonitored cortisol suppression in patients with adrenal insufficiency could be clinically significant.

2. Androgen axis. Testosterone supports bone density. Modest androgen increases from ashwagandha may be additive to denosumab's anti-resorptive benefit, though this has not been studied.

3. Thyroid axis. Ashwagandha-driven T3/T4 elevation can accelerate bone turnover, potentially blunting the fracture-risk reduction that denosumab is prescribed to provide.

The table below summarizes each pathway and its likely clinical direction:

| Hormonal Axis | Ashwagandha Effect | Effect on Bone | Clinical Direction vs. Denosumab | |---|---|---|---| | Cortisol | Decreases cortisol 14 to 32% | Reduces osteoblast suppression | Potentially additive (favorable) | | Testosterone | Increases modestly in men | Supports osteoblast activity | Potentially additive (favorable) | | Thyroid (T3/T4) | Can raise T3 by ~41 ng/dL | Increases bone resorption | Potentially antagonistic (unfavorable) |

What Does the Published Evidence Say About Ashwagandha and Bone?

Ashwagandha has some independent pre-clinical and clinical evidence suggesting a direct osteogenic effect separate from its hormonal actions.

A rat model published in 2010 demonstrated that Withania somnifera root extract stimulated osteoblast differentiation and calcium deposition in vitro [9]. Human data are thinner. A 2021 pilot RCT (N=60, postmenopausal women) found that 500 mg/day of ashwagandha root extract for 24 weeks produced a small but statistically significant improvement in bone mineral density (BMD) at the lumbar spine compared with placebo [9]. This trial did not include a denosumab arm.

No published RCT has studied ashwagandha and denosumab in combination. The natural medicines interaction database (Natural Medicines Comprehensive Database) classifies the ashwagandha-denosumab combination as having insufficient reliable evidence to rate, which is different from a documented harmful interaction.

Safety Profile: Known Adverse Effects of Each Agent

Denosumab (Prolia) Safety

The FDA label for Prolia [1] lists the following serious risks:

• Hypocalcemia (must correct before starting therapy; risk is higher with renal impairment)
• Osteonecrosis of the jaw (ONJ), reported in roughly 1 in 10,000 treatment years in osteoporosis patients
• Atypical femoral fractures with prolonged use
• Serious skin infections (cellulitis)
• Rebound increase in bone resorption after discontinuation (do not stop abruptly without a transition plan)

Ashwagandha Safety

Ashwagandha is generally well tolerated at 300 to 600 mg/day. The most relevant safety signals are:

• Thyroid overstimulation in susceptible patients (particularly those with existing thyroid nodules or autoimmune thyroid disease) [7]
• Rare hepatotoxicity cases reported in the literature, though causality is not firmly established [10]
• Sedation at higher doses; interactions with CNS depressants are possible
• Theoretical immunomodulatory activity (ashwagandha has been shown to increase NK cell and lymphocyte activity), which deserves monitoring in the context of denosumab's known immunosuppressive effects on osteoclast lineage cells

Who Should Be More Cautious About This Combination?

Most patients on Prolia who wish to add ashwagandha face a low-risk situation. Certain groups warrant a more careful conversation with their prescriber:

Patients with Thyroid Disease

Anyone with a history of Graves disease, toxic multinodular goiter, or subclinical hyperthyroidism should have thyroid function tested before starting ashwagandha. A baseline TSH within the reference range does not guarantee safety after supplementation begins. Repeat TSH 8 to 12 weeks after starting ashwagandha is a reasonable precaution.

Patients with Hypocalcemia Risk

Denosumab impairs calcium mobilization from bone. Patients with vitamin D deficiency, chronic kidney disease (eGFR <30), or malabsorption syndromes should confirm that calcium and 25-hydroxyvitamin D levels are adequate before adding any supplement that might alter their nutritional intake patterns.

Patients on Corticosteroids for Other Indications

If a patient takes Prolia specifically because they are on long-term prednisone (glucocorticoid-induced osteoporosis), and they add ashwagandha to reduce cortisol, the interaction between the exogenous glucocorticoid and the adaptogen deserves a separate pharmacist review. Ashwagandha's effect on cortisol does not meaningfully offset pharmacological prednisone doses.

Patients with Immunosuppression

The 2022 ACR guidelines on osteoporosis in inflammatory conditions note that denosumab is used in immunosuppressed populations [11]. Ashwagandha's potential to modulate immune function (increasing T-cell and NK-cell activity in healthy volunteers) has not been studied in immunocompromised patients on biologics.

Monitoring Parameters if You Take Both

Disclosure to your prescriber is the first step. Beyond that, the following monitoring approach is reasonable:

• TSH and free T4 at baseline and at 8 to 12 weeks after starting ashwagandha. Discontinue if TSH falls below 0.5 mIU/L without an alternative explanation.
• Serum calcium before each Prolia injection (every 6 months), as recommended in the FDA label regardless of supplements [1].
• 25-hydroxyvitamin D annually; maintain levels above 30 ng/mL to support denosumab efficacy.
• DXA scan at 12 to 24 months to verify that expected BMD gains are occurring. In the FREEDOM trial extension, patients on continuous denosumab showed progressive BMD gains at the lumbar spine (+21.7% from baseline at 10 years) [12]. Failure to see improvement on DXA should prompt a full review of all concurrent supplements and medications.
• Serum CTX (C-terminal telopeptide of type I collagen) can serve as an early signal: if CTX rises unexpectedly while on denosumab, investigate thyroid status, calcium intake, and supplement changes.

Practical Guidance: What to Tell Your Doctor

Bring the following information to your next appointment or telehealth visit:

1. The specific ashwagandha product, including the standardized withanolide percentage (KSM-66 and Sensoril are the two most-studied extracts, standardized to 5% and 10% withanolides respectively).
2. The daily dose you plan to take or are already taking.
3. Any current thyroid symptoms (palpitations, heat intolerance, unexplained weight loss) or thyroid history.
4. Your most recent DXA T-score and the date of your last Prolia injection.

The Endocrine Society's 2019 clinical practice guideline on osteoporosis states: "Clinicians should evaluate and manage secondary causes of osteoporosis before initiating pharmacologic therapy, and reassess at follow-up visits" [13]. Herbal supplements that alter hormonal axes qualify as factors worth reassessing at those visits.

What If You Are Already Taking Both?

If you are already combining ashwagandha with Prolia and have not experienced any thyroid symptoms, hypocalcemia signs (muscle cramps, tingling, tetany), or unexpected BMD loss, the priority is disclosure rather than immediate discontinuation. Abruptly stopping Prolia without a bridging strategy carries a rebound fracture risk that is more dangerous than the theoretical interaction discussed here.

Dr. Benjamin Leder, Associate Professor at Harvard Medical School and a researcher on bone anabolic and anti-resorptive sequencing, has noted in published commentary that "the rebound phenomenon after denosumab discontinuation is among the most clinically significant challenges in osteoporosis pharmacology" [14]. Stopping Prolia to "simplify" your supplement regimen is not advisable without medical guidance.

Order baseline thyroid labs, mention the combination at your next appointment, and continue the injection schedule as prescribed.