DangerousContraindicated
St. John's Wort
St. John's Wort can markedly lower tacrolimus concentrations and cause rejection risk.
Recommendation: Avoid completely unless the transplant team explicitly directs otherwise.
Tacrolimus
Prescription ·Strong evidence ·Reviewed May 2026
Tacrolimus is a calcineurin inhibitor used to prevent rejection after kidney, liver, heart, lung, and other organ transplants depending on formulation and protocol. It has a narrow therapeutic index and major risks including nephrotoxicity, neurotoxicity, hyperkalemia, hypomagnesemia, hypertension, diabetes, QT concerns, serious infections, malignancy, and strong CYP3A4/P-glycoprotein interactions.
What it's good for
The bottom line
Evidence rating strong. Most-documented uses: prevention of organ transplant rejection, core immunosuppressive therapy in kidney, liver, heart, and lung transplant protocols, treatment of selected refractory autoimmune conditions off-label. 3 sources indexed (1995–2026), with 5 interaction records on file.
The science
How it works, mechanistically.
Core mechanism
Tacrolimus binds FKBP-12 to form a complex that inhibits calcineurin, preventing NFAT activation and interleukin-2 transcription in T cells. This suppresses T-cell activation and transplant rejection. CYP3A4/5 and P-glycoprotein determine much of its exposure, while renal vasoconstriction and tubular effects produce nephrotoxicity and electrolyte abnormalities.2,3
Class
Calcineurin inhibitor immunosuppressant
Absorption
Fat-soluble; take with food
Dosing
Dosing & protocol.
Common range
Systemic transplant dosing is individualized by organ, formulation, genotype, interacting drugs, and target trough concentration. Immediate-release capsules are commonly divided every 12 hours; extended-release products are not interchangeable milligram-for-milligram without specialist direction.
Recommended form
Exact prescribed tacrolimus formulation with trough-guided monitoring; do not interchange immediate-release and extended-release products without specialist supervision
Take consistently with regard to food and time of day. Avoid grapefruit products and notify the transplant team before starting or stopping supplements.
Depletions
What it depletes.
Nutrients this medication can lower over time, and what to replace.
Magnesium
SignificantTacrolimus can cause renal magnesium wasting and clinically significant hypomagnesemia.
Replace Magnesium GlycinateMonitor Serum magnesiumOnset Days to months after initiation, especially post-transplant
Safety
Full safety detail.
Side effects
- Nephrotoxicity
- Tremor
- Headache
- Seizures or posterior reversible encephalopathy syndrome rarely
- Hyperkalemia
- Hypomagnesemia
- Hypertension
- New-onset diabetes after transplant
- QT prolongation risk
- Serious infections
- Lymphoma and skin cancers
- Gastrointestinal upset
Contraindications
- Known hypersensitivity to tacrolimus or formulation components2,3
- Use only under clinicians experienced with immunosuppression and therapeutic drug monitoring2
- Avoid unsupervised formulation switches
- Use caution with kidney dysfunction, hyperkalemia, QT risk, infection, malignancy risk, and interacting CYP3A4/P-gp drugs or supplements1,3
Interactions
Interaction records.
SeriousCaution
Potassium
Tacrolimus can cause hyperkalemia, and potassium supplements or salt substitutes can make levels dangerous.
Recommendation: Avoid potassium supplementation unless prescribed and monitored by the transplant team.
InfoSynergy
Magnesium Glycinate
Magnesium can help correct tacrolimus-associated hypomagnesemia when monitored.
Recommendation: Use clinician-directed dosing and monitor magnesium and kidney function.
SeriousCaution
Quercetin
Quercetin may inhibit CYP3A4 or P-glycoprotein and could increase tacrolimus exposure and toxicity.
Recommendation: Avoid high-dose quercetin unless trough levels and kidney function are monitored by the transplant team.
SeriousCaution
Berberine
Berberine may alter CYP3A or P-glycoprotein activity and make tacrolimus concentrations unpredictable.
Recommendation: Avoid unsupervised berberine; check trough levels if exposure changes are possible.
Sources
Sources, by evidence tier.
Numbered references. Citations throughout the page link here.
Reviews & position papers
2- 1KDIGO Clinical Practice Guideline for the Care of Kidney Transplant RecipientsNeeds reviewNo linkKidney Disease: Improving Global Outcomes · American Journal of Transplantation · 2009
Guideline supports therapeutic monitoring and surveillance for nephrotoxicity, electrolytes, infection, and malignancy.
- 2Tacrolimus in solid organ transplantationNeeds reviewNo linkVenkataramanan R et al. · Clinical Pharmacokinetics · 1995
Review describes pharmacokinetics, monitoring, and adverse effects.
Reference material
1- 3Tacrolimus Capsules US Prescribing InformationNeeds reviewURLU.S. National Library of Medicine · DailyMed · 2026
Labeling describes boxed warning, therapeutic drug monitoring, nephrotoxicity, hyperkalemia, infections, malignancies, and CYP3A interactions.
Keep exploring
Deep dives & adjacent profiles.
This page is educational. Do not start, stop, or change a supplement or medication based on it without checking with a qualified healthcare professional.
Use this with your stack
Tacrolimus in NutriStack.
Add it to your stack, see how it interacts with everything else you take, and get a Stack Score that updates the moment it does.