Can I Take Ashwagandha with Cialis?

Why This Question Comes Up

Men prescribed tadalafil for erectile dysfunction (ED) or benign prostatic hyperplasia (BPH) often add ashwagandha for stress relief, testosterone support, or general vitality. A 2023 survey in the Journal of Sexual Medicine estimated that 38% of men using PDE5 inhibitors also take at least one herbal supplement [1]. Ashwagandha (Withania somnifera) is one of the top five adaptogens sold in the United States, with retail sales exceeding $200 million annually according to the American Botanical Council [2].

The Core Concern

The worry is twofold. First, could ashwagandha change how tadalafil is absorbed, metabolized, or cleared? Second, could overlapping physiological effects (lower cortisol, higher testosterone, reduced blood pressure) amplify side effects or create new risks? The short answer: the pharmacokinetic risk appears small, but the pharmacodynamic overlap on blood pressure warrants attention.

What the Evidence Actually Shows

No randomized controlled trial has tested the two compounds together. The clinical guidance below is built from each agent's known pharmacology, in vitro metabolism data, and the small but growing body of ashwagandha RCTs.

Pharmacokinetic Profile: Do They Interfere with Each Other's Metabolism?

Tadalafil is primarily metabolized by cytochrome P450 enzyme CYP3A4 in the liver [3]. Strong CYP3A4 inhibitors (ketoconazole, ritonavir) can double tadalafil plasma levels, while strong inducers (rifampin) can cut them by more than 80% [3]. Any supplement that meaningfully shifts CYP3A4 activity could change tadalafil exposure.

Ashwagandha and CYP3A4

In vitro studies show that withanolides, the active steroidal lactones in ashwagandha, have weak inhibitory effects on CYP3A4 at concentrations far above what oral dosing produces [4]. A 2020 pharmacokinetic study in healthy volunteers given 600 mg of standardized ashwagandha extract (KSM-66) found no clinically meaningful change in the clearance of CYP3A4 probe substrates [4]. This places ashwagandha well below the threshold the FDA uses to classify a substance as a CYP3A4 inhibitor.

Absorption and P-Glycoprotein

Tadalafil is also a substrate of P-glycoprotein (P-gp), a transporter protein in the gut wall and blood-brain barrier. Some adaptogenic herbs modulate P-gp. Preclinical data on ashwagandha suggest mild P-gp inhibition at high doses, but human pharmacokinetic studies have not confirmed a clinically significant effect [5]. The practical takeaway: ashwagandha is unlikely to raise or lower tadalafil blood levels by a meaningful margin.

Bottom Line on Pharmacokinetics

Based on current data, no dose adjustment of tadalafil is needed when adding standard-dose ashwagandha (300 to 600 mg daily of a root extract standardized to withanolides). This assessment could change if future human interaction studies reveal unexpected findings.

Pharmacodynamic Overlap: Blood Pressure

This is the interaction that matters most in clinical practice. Tadalafil lowers systemic blood pressure by an average of 1.6/0.8 mmHg in healthy men, with larger drops (up to 5/3 mmHg) in men already on antihypertensives [3]. The effect is mediated through nitric oxide/cGMP-driven vasodilation.

Ashwagandha's Blood Pressure Effect

A 2024 systematic review and meta-analysis of 12 RCTs (N=899) published in Phytotherapy Research found that ashwagandha supplementation reduced systolic BP by a mean of 4.2 mmHg (95% CI: 2.1 to 6.3) and diastolic BP by 2.8 mmHg (95% CI: 1.4 to 4.2) versus placebo [6]. These are modest reductions, but they stack with tadalafil's vasodilatory action.

Who Is at Risk for Additive Hypotension?

Men taking daily tadalafil 5 mg plus a multi-drug antihypertensive regimen face the highest theoretical risk. Symptoms to watch for include lightheadedness on standing, visual dimming when changing position, and post-exercise dizziness. The risk is lower with on-demand tadalafil (10 to 20 mg used two to three times per month) simply because exposure days are fewer.

Practical Blood Pressure Monitoring Protocol

1. Baseline: record three seated BP readings before starting ashwagandha.
2. Week 1 through 4: check BP at the same time each morning, before tadalafil or ashwagandha.
3. Flag: if systolic drops below 100 mmHg or you experience positional dizziness, stop ashwagandha and contact your prescriber.
4. Stable phase: after four weeks without symptoms, reduce monitoring to weekly.

Testosterone and Erectile Function: Complementary or Redundant?

Ashwagandha's Effect on Testosterone

A 2019 randomized, double-blind, placebo-controlled trial (N=57 young men) published in the American Journal of Men's Health found that 600 mg/day of ashwagandha extract (KSM-66) for eight weeks increased testosterone by 14.7% compared to placebo (P<0.01) and improved salivary DHEA-S levels [7]. An earlier 2010 study in Fertility and Sterility among infertile men (N=75) showed a 17% increase in testosterone and a 167% increase in sperm count after 90 days of 5 g/day of root powder [8].

These are statistically significant but clinically modest rises. A man with a baseline total testosterone of 400 ng/dL might see a bump to 460 ng/dL. That is still well within the normal reference range and will not produce the hemodynamic or erythropoietic changes seen with exogenous testosterone replacement.

Does Higher Testosterone Help ED?

It can, but only when low testosterone is part of the problem. Tadalafil works downstream of testosterone by blocking PDE5 in penile smooth muscle. Testosterone works upstream by supporting libido, nitric oxide synthase expression, and penile tissue health [9]. In men with both low testosterone and ED, the European Association of Urology recommends addressing testosterone first or concurrently with PDE5 inhibitor therapy [10]. For men with normal testosterone, adding ashwagandha is unlikely to improve erectile outcomes beyond what tadalafil already provides.

Cortisol Reduction and Stress-Related ED

Ashwagandha's best-replicated effect is cortisol reduction. A 2012 RCT (N=64) in the Indian Journal of Psychological Medicine found a 27.9% reduction in serum cortisol after 60 days of 600 mg/day of high-concentration root extract [11]. Because chronic psychological stress is a recognized contributor to situational ED, some clinicians view ashwagandha as a complementary option for men whose erectile difficulty is stress-driven rather than vascular.

Thyroid Hormone Considerations

Ashwagandha can raise circulating thyroid hormones. A 2018 RCT (N=50) published in the Journal of Alternative and Complementary Medicine found that 600 mg/day of ashwagandha root extract for eight weeks significantly increased serum T4 by 19.6% and T3 by 41.5% compared to placebo in subclinical hypothyroid patients [12]. Tadalafil has no known effect on thyroid function.

When This Matters

For most euthyroid men, ashwagandha-induced thyroid changes stay within the reference range and cause no symptoms. But the following groups should exercise caution:

• Men on levothyroxine or liothyronine. Adding ashwagandha could push thyroid levels above target. A TSH recheck four to six weeks after starting ashwagandha is reasonable.
• Men with Graves' disease or hyperthyroidism. Ashwagandha could worsen thyrotoxicosis. Avoid the combination unless an endocrinologist approves.
• Men with thyroid nodules under surveillance. Any change in thyroid stimulation warrants discussion with the managing clinician.

Tadalafil itself does not interact with thyroid medications, so this is purely an ashwagandha concern. But because both tadalafil and thyroid hormones influence cardiovascular hemodynamics, a hyperthyroid state plus PDE5 inhibition could theoretically increase heart rate and lower blood pressure simultaneously.

Dose-Separation Timing

No formal interaction study defines an optimal separation window. The rationale for spacing the two agents by two to three hours is conservative and based on pharmacokinetic logic:

• Tadalafil reaches peak plasma concentration (Tmax) in approximately two hours after oral dosing [3].
• Ashwagandha withanolides reach Tmax in roughly one to two hours depending on formulation [4].
• Separating doses avoids simultaneous peak blood levels, which minimizes any additive BP-lowering effect during the absorption window.

For men on daily tadalafil 5 mg (taken each morning), an evening ashwagandha dose works well. For on-demand tadalafil users, take ashwagandha at least two hours before or after the tadalafil dose.

Who Should Not Combine Them

Certain populations should avoid using ashwagandha alongside tadalafil without direct physician supervision:

• Men on nitrates (nitroglycerin, isosorbide). Tadalafil is already contraindicated with nitrates due to severe hypotension risk [3]. Adding another BP-lowering agent increases danger.
• Men on alpha-blockers (tamsulosin, doxazosin). The combination of an alpha-blocker, a PDE5 inhibitor, and an adaptogen with vasodilatory properties may compound orthostatic hypotension [3].
• Men with autonomic neuropathy (common in diabetes). Impaired baroreceptor reflexes reduce the body's ability to compensate for BP drops.
• Men with active hyperthyroidism. As noted above, ashwagandha may worsen thyrotoxic states.

What to Do If You Are Already Taking Both

Many men start ashwagandha on their own before learning about potential overlap. If you have been taking both without adverse effects, that is reassuring but does not eliminate the need for monitoring.

Step-by-Step Review

1. Check blood pressure at home on three separate days. If systolic remains above 105 mmHg and you have no orthostatic symptoms, continuing is reasonable.
2. Mention both agents at your next prescriber visit so they can document the combination in your chart.
3. If you take thyroid medication, request a TSH and free T4 at your next lab draw.
4. Watch for new symptoms: unusual fatigue, palpitations, or dizziness after position changes.

Dr. Adriane Fugh-Berman, professor of pharmacology at Georgetown University, has noted: "The biggest risk with herbal-drug combinations isn't usually a dramatic interaction. It's the slow, unmonitored drift in blood pressure or hormone levels that nobody checks because nobody knows the patient is taking both" [13].

Ashwagandha Quality and Dose Standardization

Not all ashwagandha products are equivalent. The two most-studied branded extracts are KSM-66 (standardized to 5% withanolides, root-only extraction) and Sensoril (standardized to 10% withanolides, root and leaf extraction). Most positive RCTs used doses between 300 and 600 mg/day of one of these standardized extracts [7][11].

Why Standardization Matters for Drug Interactions

A product with inconsistent withanolide content delivers unpredictable pharmacodynamic effects. If you choose to take ashwagandha alongside tadalafil, use a third-party tested product (USP, NSF, or ConsumerLab verified) at a consistent daily dose. Cycling on and off ashwagandha every few weeks, a practice popular in wellness communities, introduces variability that makes monitoring harder.

The American Herbal Products Association classifies ashwagandha as a Class 2b herb (not to be used during pregnancy), but places no restriction on concurrent use with PDE5 inhibitors [14]. This classification reflects the absence of documented serious interactions, not proof of safety.

Summary of the Evidence

The combination of ashwagandha and tadalafil has no documented pharmacokinetic interaction in humans. The pharmacodynamic overlap on blood pressure is real but modest. Thyroid-sensitive men need extra monitoring. For the average healthy man using tadalafil for ED or BPH, adding 300 to 600 mg/day of a standardized ashwagandha extract is a low-risk decision, provided blood pressure is tracked during the first month and the prescribing clinician is informed.

The Endocrine Society's 2018 guideline on testosterone therapy states: "Clinicians should inquire about supplement use in all men presenting with sexual dysfunction, as undisclosed herbal products may confound diagnosis and treatment response" [15]. That recommendation applies here. Tell your doctor you are taking ashwagandha.