Melatonin and medications.
Melatonin is in the Distil supplement database, evidence Grade A. The page below lists every medication we have explicitly assessed it against.
Melatonin is the hormone your body releases as darkness falls, and supplementing it shifts the timing of your sleep clock rather than sedating you. This distinction matters. The evidence is Grade A for circadian problems: jet lag, shift work, and delayed sleep phase, where a small 0.5 to 1mg dose taken at the right time can nudge the clock back into line. In the UK, melatonin is a prescription-only medicine rather than an over-the-counter supplement, so it is something to raise with a GP rather than to buy. For general "I can't sleep" complaints the evidence is only Grade C, and for that, magnesium glycinate with L-theanine is worth trying first. Higher doses can shorten how long it takes to fall asleep but do not improve overall sleep quality, and they mostly add morning grogginess and vivid dreams, so a low dose is the sensible default. It is not designed as a nightly long-term habit. On interactions, separate it from or be cautious with sedatives and benzodiazepines because of additive drowsiness, monitor it alongside anticoagulants, and treat SSRIs as a reason for caution. Used for the right reason, at a low dose, at the right hour, it earns its place.
Below are the 31 documented pairs we have explicitly assessed for Melatonin: 31 amber. The pairs cluster around 6 mechanisms: Additive blood-pressure lowering, Additive CNS sedation, Reduced blood-pressure-medicine effect, CYP1A2 inhibition, Reduced glucose control, and Immune-stimulant vs immunosuppressant (precautionary). 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
Last reviewed 15 June 2026. Each interaction below lists the evidence its assessment drew on: some rest on studies of the exact pair, others on mechanism evidence, where a citation may support one part of the reasoning rather than the exact combination. The evidence line on each entry says which.
Additive blood-pressure lowering
Amber Does interact with Bisoprolol?
Taken at night, melatonin can modestly lower blood pressure during sleep. Combined with a blood-pressure medicine like bisoprolol this may add up to a slightly larger drop than the medicine alone. There is also a second point worth knowing: beta-blockers such as bisoprolol can suppress your own natural melatonin, so some people taking them sleep better when melatonin is added. Either way, if you notice dizziness, check your blood pressure and mention it to your prescriber.
Evidence: Based on an established mechanism, with no direct study of this exact combination yet.
Reviewer-flagged: awaiting clinical-reviewer sign-off.
Amber Does interact with Diltiazem hydrochloride?
Taken at night, melatonin can modestly lower blood pressure during sleep. Combined with a blood-pressure medicine like diltiazem this may add up to a slightly larger drop than the medicine alone. This is usually mild and often welcome, but if you notice dizziness or lightheadedness, check your blood pressure and mention it to your prescriber.
Evidence: Based on an established mechanism, with no direct study of this exact combination yet.
Reviewer-flagged: awaiting clinical-reviewer sign-off.
Amber Does interact with Doxazosin mesilate?
Taken at night, melatonin can modestly lower blood pressure during sleep. Combined with a blood-pressure medicine like doxazosin this may add up to a slightly larger drop than the medicine alone. Doxazosin can already cause dizziness on standing, so if you notice this, check your blood pressure and mention it to your prescriber.
Evidence: Based on an established mechanism, with no direct study of this exact combination yet.
Reviewer-flagged: awaiting clinical-reviewer sign-off.
Amber Does interact with Furosemide?
Taken at night, melatonin can modestly lower blood pressure during sleep. Combined with a blood-pressure or fluid medicine like furosemide this may add up to a slightly larger drop than the medicine alone. This is usually mild, but if you notice dizziness or lightheadedness, check your blood pressure and mention it to your prescriber.
Evidence: Based on an established mechanism, with no direct study of this exact combination yet.
Reviewer-flagged: awaiting clinical-reviewer sign-off.
Amber Does interact with Indapamide?
Taken at night, melatonin can modestly lower blood pressure during sleep. Combined with a blood-pressure medicine like indapamide this may add up to a slightly larger drop than the medicine alone. This is usually mild and often welcome, but if you notice dizziness or lightheadedness, check your blood pressure and mention it to your prescriber.
Evidence: Based on an established mechanism, with no direct study of this exact combination yet.
Reviewer-flagged: awaiting clinical-reviewer sign-off.
Amber Does interact with Losartan?
Taken at night, melatonin can modestly lower blood pressure during sleep. Combined with a blood-pressure medicine like losartan this may add up to a slightly larger drop than the medicine alone. This is usually mild and often welcome, but if you notice dizziness or lightheadedness, check your blood pressure and mention it to your prescriber.
Evidence: Based on an established mechanism, with no direct study of this exact combination yet.
Reviewer-flagged: awaiting clinical-reviewer sign-off.
Amber Does interact with Ramipril?
Taken at night, melatonin can modestly lower blood pressure during sleep. Combined with a blood-pressure medicine like ramipril this may add up to a slightly larger drop than the medicine alone. This is usually mild and often welcome, but if you notice dizziness or lightheadedness, check your blood pressure and mention it to your prescriber.
Evidence: Based on an established mechanism, with no direct study of this exact combination yet.
Reviewer-flagged: awaiting clinical-reviewer sign-off.
Amber Does interact with Spironolactone?
Taken at night, melatonin can modestly lower blood pressure during sleep. Combined with a blood-pressure medicine like spironolactone this may add up to a slightly larger drop than the medicine alone. This is usually mild and often welcome, but if you notice dizziness or lightheadedness, check your blood pressure and mention it to your prescriber.
Evidence: Based on an established mechanism, with no direct study of this exact combination yet.
Reviewer-flagged: awaiting clinical-reviewer sign-off.
Additive CNS sedation
Amber Does interact with Agomelatine?
Agomelatine is a prescription antidepressant that acts on the same melatonin receptors as a melatonin supplement, so taking melatonin on top may add to the sleep-promoting effect. There is no direct study of the two together, so this is a cautionary note rather than a firm rule. Agomelatine also needs liver-function monitoring, which is a separate reason to keep your prescriber informed of anything you add.
Evidence: Based on an established mechanism, with no direct study of this exact combination yet.
Reviewer-flagged: awaiting clinical-reviewer sign-off.
Amber Does interact with Alprazolam?
Melatonin and alprazolam 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 or operating machinery.
Evidence: Based on an established mechanism, with no direct study of this exact combination yet.
Reviewer-flagged: awaiting clinical-reviewer sign-off.
Amber Does interact with Clonidine?
Melatonin and clonidine 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 interact with Diazepam?
Melatonin and diazepam 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 or operating machinery.
Evidence: Based on an established mechanism, with no direct study of this exact combination yet.
Reviewer-flagged: awaiting clinical-reviewer sign-off.
Amber Does interact with Guanfacine?
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 interact with Lorazepam?
Melatonin and lorazepam 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 interact with Temazepam?
Melatonin and temazepam are both used to help with sleep, so taking them together may mean deeper-than-intended nocturnal sedation and a heavier morning hangover. Use with care.
Evidence: Based on an established mechanism, with no direct study of this exact combination yet.
Reviewer-flagged: awaiting clinical-reviewer sign-off.
Reduced blood-pressure-medicine effect
Amber Does interact with Amlodipine?
Melatonin has been shown to raise blood pressure and heart rate in people taking the related blood-pressure drug nifedipine, working against it. Amlodipine is in the same drug family, so the same effect may apply. If you take amlodipine, it is worth discussing melatonin with your prescriber and monitoring your blood pressure rather than starting it on your own.
Evidence: Based on an established mechanism, with no direct study of this exact combination yet.
Reviewer-flagged: awaiting clinical-reviewer sign-off.
Amber Does interact with Felodipine?
Melatonin has been shown to raise blood pressure and heart rate in people taking the related blood-pressure drug nifedipine, working against it. Felodipine is in the same drug family, so the same effect may apply. If you take felodipine, it is worth discussing melatonin with your prescriber and monitoring your blood pressure rather than starting it on your own.
Evidence: Based on an established mechanism, with no direct study of this exact combination yet.
Reviewer-flagged: awaiting clinical-reviewer sign-off.
Amber Does interact with Lacidipine?
Melatonin has been shown to raise blood pressure and heart rate in people taking the related blood-pressure drug nifedipine, working against it. Lacidipine is in the same drug family, so the same effect may apply. If you take lacidipine, it is worth discussing melatonin with your prescriber and monitoring your blood pressure rather than starting it on your own.
Evidence: Based on an established mechanism, with no direct study of this exact combination yet.
Reviewer-flagged: awaiting clinical-reviewer sign-off.
Amber Does interact with Lercanidipine hydrochloride?
Melatonin has been shown to raise blood pressure and heart rate in people taking the related blood-pressure drug nifedipine, working against it. Lercanidipine is in the same drug family, so the same effect may apply. If you take lercanidipine, it is worth discussing melatonin with your prescriber and monitoring your blood pressure rather than starting it on your own.
Evidence: Based on an established mechanism, with no direct study of this exact combination yet.
Reviewer-flagged: awaiting clinical-reviewer sign-off.
Amber Does interact with Nifedipine?
In people whose blood pressure is well controlled on nifedipine, taking melatonin in the evening has been shown to raise blood pressure and heart rate, which works against what the nifedipine is doing. If you take nifedipine for blood pressure, it is worth discussing melatonin with your prescriber and monitoring your readings rather than starting it on your own.
Evidence: Supported by human study data.
CYP1A2 inhibition
Amber Does interact with Ciprofloxacin?
Ciprofloxacin slows the liver enzyme that clears melatonin, so taking the two together may push melatonin levels higher than the dose alone suggests and lead to more next-day grogginess. A short course of ciprofloxacin is usually self-limiting, but a lower melatonin dose during the course is a sensible precaution.
Evidence: Based on an established mechanism, with no direct study of this exact combination yet.
Reviewer-flagged: awaiting clinical-reviewer sign-off.
Amber Does interact with Fluvoxamine?
Fluvoxamine slows the liver enzyme that clears melatonin, so taking the two together can push melatonin levels far higher than the dose alone suggests. This may mean stronger next-morning grogginess and heavier sedation. If you take fluvoxamine, a much lower melatonin dose tends to be enough, and it is worth raising with your prescriber first.
Evidence: Supported by human study data.
Reduced glucose control
Amber Does interact with Dapagliflozin?
Melatonin can blunt the body's insulin response and raise blood sugar after eating, which works against the blood-sugar control that dapagliflozin is helping with. The effect is strongest when melatonin and food are taken close together, so if you take dapagliflozin it is best to keep melatonin well away from your evening meal and to mention it to your prescriber if your blood sugar is being monitored.
Evidence: Based on an established mechanism, with no direct study of this exact combination yet.
Reviewer-flagged: awaiting clinical-reviewer sign-off.
Amber Does interact with Gliclazide?
Melatonin can blunt the body's insulin response and raise blood sugar after eating, which works against a diabetes medicine like gliclazide that is trying to lower it. The effect is strongest when melatonin and food are taken close together, so if you take gliclazide it is best to keep melatonin well away from your evening meal and to mention it to your prescriber, especially if your blood sugar is being monitored.
Evidence: Supported by human study data.
Amber Does interact with Glimepiride?
Melatonin can blunt the body's insulin response and raise blood sugar after eating, which works against a diabetes medicine like glimepiride that is trying to lower it. The effect is strongest when melatonin and food are taken close together, so if you take glimepiride it is best to keep melatonin well away from your evening meal and to mention it to your prescriber, especially if your blood sugar is being monitored.
Evidence: Based on an established mechanism, with no direct study of this exact combination yet.
Reviewer-flagged: awaiting clinical-reviewer sign-off.
Amber Does interact with Insulin glargine?
Melatonin can blunt the body's insulin response and raise blood sugar after eating, which can make blood-sugar control on insulin glargine a little harder. The effect is strongest when melatonin and food are taken close together, so if you use insulin it is best to keep melatonin well away from your evening meal, watch your readings, and mention it to your diabetes team rather than starting it on your own.
Evidence: Based on an established mechanism, with no direct study of this exact combination yet.
Reviewer-flagged: awaiting clinical-reviewer sign-off.
Amber Does interact with Metformin?
Melatonin can blunt the body's insulin response and raise blood sugar after eating, which works against the blood-sugar control that metformin is helping with. The effect is strongest when melatonin and food are taken close together, so if you take metformin it is best to keep melatonin well away from your evening meal and to mention it to your prescriber if your blood sugar is being monitored.
Evidence: Supported by human study data.
Amber Does interact with Pioglitazone hydrochloride?
Melatonin can blunt the body's insulin response and raise blood sugar after eating, which works against the blood-sugar control that pioglitazone is helping with. The effect is strongest when melatonin and food are taken close together, so if you take pioglitazone it is best to keep melatonin well away from your evening meal and to mention it to your prescriber if your blood sugar is being monitored.
Evidence: Based on an established mechanism, with no direct study of this exact combination yet.
Reviewer-flagged: awaiting clinical-reviewer sign-off.
Amber Does interact with Sitagliptin?
Melatonin can blunt the body's insulin response and raise blood sugar after eating, which works against the blood-sugar control that sitagliptin is helping with. The effect is strongest when melatonin and food are taken close together, so if you take sitagliptin it is best to keep melatonin well away from your evening meal and to mention it to your prescriber if your blood sugar is being monitored.
Evidence: Based on an established mechanism, with no direct study of this exact combination yet.
Reviewer-flagged: awaiting clinical-reviewer sign-off.
Immune-stimulant vs immunosuppressant (precautionary)
Amber Does interact with Ciclosporin?
Melatonin can stimulate parts of the immune system, which in theory works against medicines like ciclosporin that are deliberately suppressing it, for example after a transplant. There is no direct study of the two together, but because the stakes are high it is best not to start melatonin without clearing it with the team that manages your ciclosporin.
Evidence: Based on an established mechanism, with no direct study of this exact combination yet.
Reviewer-flagged: awaiting clinical-reviewer sign-off.
Amber Does interact with Tacrolimus?
Melatonin can stimulate parts of the immune system, which in theory works against medicines like tacrolimus that are deliberately suppressing it, for example after a transplant. There is no direct study of the two together, but because the stakes are high it is best not to start melatonin without clearing it with the team that manages your tacrolimus.
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. Use the checker below to surface any medication, 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.
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