What happens when you take cbd with tacrolimus?
Tacrolimus is a calcineurin inhibitor used after solid organ transplant (kidney, liver, heart, lung) and for some autoimmune conditions. It has a notoriously narrow therapeutic window: too low and the graft is rejected, too high and patients develop tremor, hypertension, hyperglycemia, kidney injury, neurotoxicity, and infections from over-immunosuppression. Tacrolimus is cleared primarily by intestinal and hepatic CYP3A4 and CYP3A5 and is also a substrate of the efflux pump P-glycoprotein (P-gp) in the gut wall.
Cannabidiol (CBD) inhibits all three pathways. In a frequently cited case report published in the American Journal of Transplantation, a patient enrolled in a CBD trial for epilepsy who was also taking tacrolimus showed an approximately 3-fold rise in dose-normalized tacrolimus trough levels after CBD escalation to 2000-2900 mg/day, requiring tacrolimus dose reductions to avoid toxicity. Subsequent case reports in kidney and liver transplant recipients have described tacrolimus toxicity (acute kidney injury, tremor, neurotoxicity) precipitated by over-the-counter CBD oil at much lower doses, and a more recent Phase I pharmacokinetic trial has confirmed clinically meaningful tacrolimus exposure increases with CBD co-administration.
Why is this important?
In transplant medicine, drug interactions that affect calcineurin inhibitor levels are taken extremely seriously because the consequences land on either side of a narrow band. A doubling of tacrolimus exposure can cause acute kidney injury and disabling tremor within days; a sudden drop (for example, if CBD is stopped abruptly after the dose has been reduced) can precipitate acute rejection. CBD is now widely marketed in dispensaries, wellness shops, and online stores - including to older adults with arthritis or sleep complaints, who are also a growing share of transplant recipients. Many patients do not consider CBD a 'real' medication and do not mention it on intake forms.
The interaction is not limited to ultra-high anti-seizure doses. The kidney transplant case literature describes meaningful tacrolimus rises with consumer CBD products at 100-300 mg/day. Full-spectrum hemp oils that also contain THC add further CYP3A4 inhibition. Because tacrolimus is dosed twice daily and titrated to trough levels, the interaction also confounds routine dose adjustments: a transplant team may see a high trough, lower the dose, then watch troughs crash if the patient stops the CBD without telling anyone.
What should you do?
This interaction belongs squarely in the critical category for solid organ transplant recipients.
- Tell your transplant team before any CBD use - this includes prescription Epidiolex, over-the-counter CBD oils, gummies, vapes, hemp-derived softgels, and even high-CBD topicals used over large skin areas.
- Treat CBD changes like dose changes: every initiation, dose escalation, brand switch, or discontinuation should trigger a tacrolimus trough check within 3-5 days.
- Do not stop CBD abruptly once tacrolimus has been re-titrated around it - troughs can drop quickly and put the graft at risk.
- Watch for tacrolimus toxicity symptoms: new or worsening tremor, headache, insomnia, tingling in the hands or feet, high blood pressure, reduced urine output, swelling, or new mental status changes. Contact the transplant clinic immediately.
- Apply the same caution to cyclosporine, sirolimus, and everolimus, which share CYP3A4/P-gp pathways and have documented CBD interactions in the transplant literature.
Which specific products are affected?
The interaction has been documented for both pharmaceutical Epidiolex (cannabidiol oral solution) and consumer CBD products including tinctures, capsules, gummies, sublingual sprays, and vape products. Tacrolimus is sold as Prograf, Astagraf XL, Envarsus XR, Hecoria, and various generics; the immediate-release and extended-release formulations are equally affected because the interaction is at the level of metabolism, not absorption. Cyclosporine (Neoral, Sandimmune, Gengraf), sirolimus (Rapamune), and everolimus (Zortress, Afinitor) share the same vulnerabilities. Patients on cannabis products containing both CBD and THC should be treated as having a larger and more variable interaction.
The bottom line
CBD reliably raises tacrolimus exposure through CYP3A4/3A5 and P-glycoprotein inhibition, with published case reports showing 3-fold increases in trough levels and clinical toxicity. Solid organ transplant recipients should not use any CBD product - prescription or over-the-counter - without the transplant team's explicit involvement, and any change in CBD use should trigger tacrolimus level monitoring and clinical assessment for toxicity.