Supplements and Insulin glargine.
Insulin glargine, sold under the brand names Lantus, Toujeo, Abasaglar, Semglee, is insulin replacement therapy for type 1 or insulin-requiring type 2 diabetes.
Insulin glargine is insulin replacement therapy. It is used universally in type 1 diabetes and in type 2 diabetes that has progressed to needing insulin. The supplement surface is small, because insulin is a peptide with no CYP metabolism and no plasma protein displacement story. The clinically important issue is anything that affects glucose handling. Berberine. Cinnamon (at habitual food amounts not clinically significant; at extract doses a small additive effect). Chromium at high doses. Alpha lipoic acid. And the GLP-1 mimetic supplement category. All carry small additive glycaemic effects that, stacked on top of an insulin regimen, can drive hypoglycaemia. Patients on insulin who add such a supplement benefit from more frequent glucose monitoring in the first two to four weeks of the change. Vitamin B12 status matters too, because most Type 2 patients carry metformin alongside their insulin.
Below are the 13 documented pairs we have explicitly assessed against Insulin glargine in the Distil database: 13 amber. The pairs cluster around 2 mechanisms: Reduced glucose control and Additive glucose lowering. 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
Reduced glucose control
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.
Reviewer-flagged: awaiting clinical-reviewer sign-off.
Additive glucose lowering
Alpha lipoic acid may improve how your body responds to insulin, which can lower blood sugar on top of the insulin you inject. This may increase the chance of glucose going too low. If you take alpha lipoic acid 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.
Berberine lowers blood sugar on its own. On top of insulin, which can already cause low blood sugar, the effect adds up. If you take both, monitor your glucose more closely when starting berberine and tell your diabetes team, as your insulin dose may need reducing.
Oat beta-glucan slows the rise in blood sugar after meals and can modestly lower blood sugar over time. Insulin already lowers blood sugar, so adding regular beta-glucan can add to its effect and increase the chance of a low. If you start taking it regularly, monitor your glucose more closely across the day and speak to your diabetes team, who may need to adjust your insulin dose.
Chromium may improve how your body responds to insulin, which can lower blood sugar on top of the insulin you inject. This may increase the chance of glucose going too low. If you take chromium 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, 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.
Holy basil (tulsi) may lower blood sugar on its own, on top of the insulin you inject. This may increase the chance of glucose going too low. If you take holy basil 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.
NMN may modestly improve how your body responds to insulin. If you inject insulin, the two together could in theory lower blood sugar more than your current dose is set for. This has not been studied directly. If you take both, monitor your blood sugar and speak to your diabetes team before starting.
Reviewer-flagged: awaiting clinical-reviewer sign-off.
Ginseng can lower blood sugar a little on its own. Insulin is a strong blood-sugar-lowering medicine, so adding ginseng may increase the chance of a hypo. If you use insulin, monitor your blood sugar more closely when you start or stop ginseng, and your doctor may need to adjust your insulin dose.
Reviewer-flagged: awaiting clinical-reviewer sign-off.
Pine bark extract (pycnogenol) may lower blood sugar a little on its own, on top of the insulin you inject. This may increase the chance of glucose going too low. If you take pine bark extract 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.
Psyllium lowers blood sugar on its own, so adding it to insulin can add to insulin's effect and increase the chance of a low. If you start taking psyllium regularly, monitor your glucose more closely across the day and speak to your diabetes team, who may need to adjust your insulin dose.
Reviewer-flagged: awaiting clinical-reviewer sign-off.
Saffron can modestly lower blood sugar on top of the insulin you inject, which may increase the chance of glucose going too low. If you take saffron with insulin, monitor your blood glucose closely, especially early on, and your doctor may need to adjust your insulin dose.
Reviewer-flagged: awaiting clinical-reviewer sign-off.
Milk thistle (silymarin) may lower blood sugar by improving how your body responds to insulin, which can add to the insulin you inject and increase the chance of glucose going too low. If you take silymarin 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.
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.
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.
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- the evidence-backed compounds worth adding, and the ones worth dropping
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