Garlic Extract and medications.
Garlic Extract is in the Distil supplement database, evidence Grade A. The page below lists every medication we have explicitly assessed it against.
Garlic extract has some of the strongest evidence of any supplement for lowering blood pressure, a Grade A result, with Grade B support for cholesterol and immune effects. The form matters more than almost anything else here: aged garlic extract, sold as Kyolic, is what the trials used, and raw garlic or ordinary garlic powder is not a fair substitute for the cardiovascular effect. Ried 2016 pooled the trials and confirmed a meaningful drop in blood pressure. Typical doses are 600 to 1,200mg of aged extract or an allicin-standardised product. The interaction profile is the main thing to watch. Its allicin and ajoene give it a mild antiplatelet effect, so it needs monitoring alongside anticoagulants and should be stopped six weeks before surgery, the same rule used for omega-3, vitamin E, and ginkgo. It can also lower levels of the HIV drug saquinavir. Choose the aged form, mind the surgery window, and it does real work for blood pressure.
Below are the 23 documented pairs we have explicitly assessed for Garlic Extract: 23 amber. The pairs cluster around 4 mechanisms: Additive blood-pressure lowering, Additive antiplatelet effect, Additive glucose lowering, and P-glycoprotein interaction. Every call is cited to either a clinical reference (PMID) or the British National Formulary. Anything not listed here is either still to be assessed or beyond our database scope. The checker beneath surfaces assessments by medication, and the missing-item form at the bottom of the page routes any uncatalogued medication into our next curation pass.
Documented interactions
Additive blood-pressure lowering
Garlic supplements mildly lower blood pressure, and amlodipine lowers it too. The combined effect tends to be a little larger than either alone. It is usually manageable, but watch for dizziness on standing or ankle swelling in the first couple of weeks, and tell your GP if symptoms appear.
Garlic supplements mildly lower blood pressure, and bisoprolol lowers it too. The combined effect is small but real. Watch for dizziness on standing in the first couple of weeks and tell your GP if it happens.
Garlic supplements have a mild blood-pressure-lowering effect of their own, and clonidine 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.
Reviewer-flagged: awaiting clinical-reviewer sign-off.
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.
Reviewer-flagged: awaiting clinical-reviewer sign-off.
Garlic supplements have a mild blood-pressure-lowering effect, and indapamide lowers blood pressure as well. The combined effect tends to be slightly larger. Watch for dizziness on standing in the first couple of weeks and tell your GP if symptoms appear.
Garlic supplements have a mild blood-pressure-lowering effect, and losartan lowers blood pressure as well. Together the combined effect tends to be slightly larger. It is usually manageable, but watch for dizziness on standing in the first couple of weeks and mention it to your GP if it happens.
Garlic supplements have a mild blood-pressure-lowering effect of their own, and ramipril 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.
Additive antiplatelet effect
Garlic supplements can thin the blood by reducing how well platelets clump, which adds to the blood-thinning effect of acenocoumarol and may raise bleeding risk. Culinary amounts of garlic are not the concern; concentrated extracts are. If you take acenocoumarol, discuss garlic supplements with your anticoagulant clinic and watch for easy bruising or bleeding.
Reviewer-flagged: awaiting clinical-reviewer sign-off.
Garlic has mild blood-thinning activity that can add to aspirin's. The combination is usually fine at culinary doses but stop high-dose garlic supplements at least a week before surgery.
Garlic has mild blood-thinning activity that can add to clopidogrel's. Stop high-dose garlic supplements at least a week before any surgery and tell your GP if you take garlic alongside clopidogrel long-term.
High-dose garlic extract has its own mild antiplatelet effect on top of diclofenac's. For occasional pain relief at standard doses, this is rarely a problem. For chronic NSAID use or pre-surgery, the combined effect can mean more bleeding and bruising.
High-dose garlic extract has its own mild antiplatelet effect on top of ibuprofen's. For occasional pain relief at standard doses, this is rarely a problem. For chronic NSAID use or pre-surgery, the combined effect can mean more bleeding and bruising. Stop garlic supplements at least one week before any planned surgery.
High-dose garlic extract has its own mild antiplatelet effect on top of naproxen's. For occasional pain relief at standard doses, this is rarely a problem. For chronic NSAID use or pre-surgery, the combined effect can mean more bleeding and bruising.
Garlic at supplement doses has a mild blood-thinning effect of its own. Combined with warfarin, that can shift INR. If you take both, mention the garlic supplement to whoever monitors your INR and do not stop or start without telling them.
Additive glucose lowering
Garlic supplements may lower blood sugar a little on their own. Dapagliflozin also lowers blood sugar but rarely pushes it too low on its own, so the combination is generally manageable. Monitor your glucose when you start a garlic supplement or change the dose.
Reviewer-flagged: awaiting clinical-reviewer sign-off.
Garlic supplements may lower blood sugar a little on their own. Empagliflozin also lowers blood sugar but rarely pushes it too low on its own, so the combination is generally manageable. Monitor your glucose when you start a garlic supplement or change the dose.
Reviewer-flagged: awaiting clinical-reviewer sign-off.
Garlic supplements may lower blood sugar a little on their own. Gliclazide already lowers blood sugar and carries one of the higher risks of pushing it too low among the common diabetes tablets, so taking the two together may add up. If you take both, monitor your blood glucose, especially in the first few weeks, and your doctor may need to adjust the gliclazide dose.
Reviewer-flagged: awaiting clinical-reviewer sign-off.
Garlic supplements may lower blood sugar a little on their own. Glimepiride already lowers blood sugar and can push it too low, so taking the two together may add up. If you take both, monitor your blood glucose, especially in the first few weeks, and your doctor may need to adjust the glimepiride dose.
Reviewer-flagged: awaiting clinical-reviewer sign-off.
Garlic supplements may lower blood sugar a little on their own, on top of the insulin you inject. This may increase the chance of glucose going too low. If you take a garlic supplement with insulin, monitor your blood glucose closely, especially early on, and your doctor may need to reduce your insulin dose.
Reviewer-flagged: awaiting clinical-reviewer sign-off.
Garlic supplements may lower blood sugar a little on their own. Metformin also lowers blood sugar, so the two may add up. The combination is generally manageable because metformin on its own rarely causes low blood sugar, but monitor your glucose when you start a garlic supplement or change the dose, and your doctor may adjust the metformin if needed.
Reviewer-flagged: awaiting clinical-reviewer sign-off.
Garlic supplements may lower blood sugar a little on their own. Pioglitazone also lowers blood sugar but rarely pushes it too low on its own, so the combination is generally manageable. Monitor your glucose when you start a garlic supplement or change the dose.
Reviewer-flagged: awaiting clinical-reviewer sign-off.
Garlic supplements may lower blood sugar a little on their own. Sitagliptin also lowers blood sugar but rarely pushes it too low on its own, so the combination is generally manageable. Still, monitor your glucose when you start a garlic supplement or change the dose.
Reviewer-flagged: awaiting clinical-reviewer sign-off.
P-glycoprotein interaction
Garlic supplements can lower the level of saquinavir in the blood, which may make it less effective at controlling HIV when saquinavir is used as the only protease inhibitor. In a study, garlic cut saquinavir levels by about half. If you take saquinavir, discuss garlic supplements with your HIV team rather than starting them on your own. Normal culinary garlic is a smaller concern than concentrated supplements.
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. Use the checker below to surface any medication, and submit a missing item if you take something we have not catalogued.
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-backed compounds worth adding, and the ones worth dropping
It's a paid report: £79, or £49 for the first 25 customers. The interactions check is one section of it, and you can read a real one in full before you buy.
See a real sample reportSomething missing?
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.