Supplements and Guanfacine.
Guanfacine, sold under the brand name Intuniv, is classified under "adhd non stimulant" in the BNF.
Guanfacine (brand names Intuniv) sits in the Distil medication database. The BNF classifies it under "adhd non stimulant". This means it sits outside the high-volume therapeutic classes (statins, PPIs, ACE inhibitors, SSRIs) where supplement-interaction surfaces are densely studied, and the published evidence base for specific supplement pairs is correspondingly thinner. Where interactions are documented in the Distil database, they are listed below with their clinical-reference citation; where pairs have not been explicitly assessed, the missing-item form at the bottom of the page routes them into our next curation pass. Anyone combining Guanfacine with a regular supplement stack benefits from explicit GP or pharmacist awareness rather than assuming no interaction exists by default.
Below are the 10 documented pairs we have explicitly assessed against Guanfacine in the Distil database: 10 amber. The pairs cluster around 2 mechanisms: Additive blood-pressure lowering and Additive CNS sedation. Every call is cited to either a clinical reference (PMID) or the British National Formulary. Anything not on this list is either still to be assessed or beyond our database scope. The checker beneath surfaces assessments by supplement, and the missing-item form at the bottom of the page routes any uncatalogued supplement into our next curation pass.
Documented interactions
Last reviewed 15 June 2026. Each interaction below is assessed against PubMed-indexed evidence.
Additive blood-pressure lowering
Amber Does Beetroot Extract interact with ?
Beetroot lowers blood pressure through the nitric oxide pathway, and guanfacine lowers it by reducing the nerve signals that drive blood pressure up. Used together, the combined effect tends to be a little larger than either alone. Watch for dizziness on standing, especially in the first two weeks. If symptoms appear, tell your GP.
Evidence: Limited human data, based on case reports and a known mechanism.
Reviewer-flagged: awaiting clinical-reviewer sign-off.
Amber Does Garlic Extract interact with ?
Garlic supplements have a mild blood-pressure-lowering effect of their own, and guanfacine lowers blood pressure too. Taken together the combined effect tends to be a little larger. It is usually manageable, but watch for dizziness on standing in the first couple of weeks, and tell your GP if it happens.
Evidence: Limited human data, based on case reports and a known mechanism.
Reviewer-flagged: awaiting clinical-reviewer sign-off.
Amber Does Hibiscus Extract interact with ?
Hibiscus tends to lower blood pressure on its own, and guanfacine lowers it too. Taken together the blood-pressure effects may stack, so watch for dizziness on standing, especially in the first couple of weeks. If symptoms appear, tell your GP.
Evidence: Limited human data, based on case reports and a known mechanism.
Reviewer-flagged: awaiting clinical-reviewer sign-off.
Amber Does L-Citrulline interact with ?
L-citrulline mildly lowers blood pressure by raising nitric oxide, and guanfacine lowers it by reducing the nerve signals that drive blood pressure up. Taken together the effects may stack, so watch for dizziness on standing, especially in the first couple of weeks. The added effect tends to be modest. If symptoms appear, tell your GP.
Evidence: Limited human data, based on case reports and a known mechanism.
Reviewer-flagged: awaiting clinical-reviewer sign-off.
Amber Does Taurine interact with ?
Taurine tends to lower blood pressure on its own, and guanfacine lowers it too. Taken together the blood-pressure effects may stack, so watch for dizziness on standing, especially in the first couple of weeks. The added effect tends to be modest. If symptoms appear, tell your GP.
Evidence: Limited human data, based on case reports and a known mechanism.
Reviewer-flagged: awaiting clinical-reviewer sign-off.
Additive CNS sedation
Amber Does Ashwagandha interact with ?
Ashwagandha can have a calming, mildly sedating effect and improves sleep for some people, and guanfacine commonly causes drowsiness and tiredness. Taken together they may add to the sedation. Use with care, particularly around driving, and especially in the first weeks.
Evidence: Based on an established mechanism, with no direct study of this exact combination yet.
Reviewer-flagged: awaiting clinical-reviewer sign-off.
Amber Does Lemon Balm interact with ?
Lemon balm can make you drowsy, and guanfacine commonly causes drowsiness and tiredness too. Taken together they may add to the sedation and slow your reactions more than either alone. Use with care, particularly around driving, and especially in the first weeks.
Evidence: Based on an established mechanism, with no direct study of this exact combination yet.
Reviewer-flagged: awaiting clinical-reviewer sign-off.
Amber Does Melatonin interact with ?
Melatonin and guanfacine can both promote drowsiness, so taking them together may add to the sedation and slow your reaction time more than either does alone. Use with care, particularly around driving.
Evidence: Based on an established mechanism, with no direct study of this exact combination yet.
Reviewer-flagged: awaiting clinical-reviewer sign-off.
Amber Does Passionflower interact with ?
Passionflower can make you drowsy, and guanfacine commonly causes drowsiness and tiredness too. Taken together they may add to the sedation and slow your reactions more than either alone. Use with care, particularly around driving, and especially in the first weeks.
Evidence: Based on an established mechanism, with no direct study of this exact combination yet.
Reviewer-flagged: awaiting clinical-reviewer sign-off.
Amber Does Valerian Root interact with ?
Valerian can make you drowsy, and guanfacine commonly causes drowsiness and tiredness too. Taken together they may add to the sedation and slow your reactions more than either alone. Use with care, particularly around driving or operating machinery, and especially in the first weeks.
Evidence: Based on an established mechanism, with no direct study of this exact combination yet.
Reviewer-flagged: awaiting clinical-reviewer sign-off.
What this list does not say. Pairs not flagged here are not implicitly safe. They are either not yet in our database, or fall outside our inclusion scope (food-supplement interactions only; for drug-drug interactions, the BNF is authoritative). Use the checker below to surface any supplement, and submit a missing item if you take something we have not catalogued.
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How we grade severity, choose what's in scope, and what we exclude.
Every call on this page is reasoned. We publish the full rubric for severity tiers, the medication inclusion logic, the evidence grades we accept, and what we deliberately leave out. About three thousand words. Worth reading once if you use this tool more than occasionally.
Read the full methodologyWant this checked across everything you take?
This page checks the pairs you enter. The personalised Distil report goes further:
- the same graded, cited interaction check across your whole stack, not just the pairs you thought to type in
- where your current routine may be leaving you short of your goals
- the evidence-graded compounds worth adding, and the ones worth dropping
It's a paid report: £79, or £49 founder pricing while we earn our first reviews. The interactions check is one section of it, and you can read a real one in full before you decide.
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If a supplement or medication you take isn't in our autocomplete, tell us. We go through what people flag every week and add what's missing.