Drug & supplement interaction

Melatonin + Insulin Glargine (rDNA)

Insulin Glargine (rDNA) brand name: Lantus.

Moderate Interaction
Medically reviewed by · Updated September 2026
The bottom line Moderate

Melatonin has a moderate interaction with Insulin Glargine (rDNA). Theoretically, taking melatonin with antidiabetes drugs might increase the risk of hypoglycemia.

Read the full interaction report
SeverityModerate
LikelihoodPossible
EvidenceB
What do Severity, Likelihood & Evidence mean?
Know someone taking this? Share
Facebook Post Reddit Email
On this page
Interaction report

Melatonin and Insulin Glargine (rDNA)

Here is the interaction we found between these two, with the evidence behind it.

Moderate

ANTIDIABETES DRUGS

Why this applies to Insulin Glargine (rDNA)

Insulin Glargine (rDNA) falls under ANTIDIABETES DRUGS — the group Melatonin interacts with.

Theoretically, taking melatonin with antidiabetes drugs might increase the risk of hypoglycemia.
Some clinical research shows that melatonin reduces levels of fasting blood glucose and improves glycemic control. However, other research suggests that melatonin might impair glucose utilization and increase insulin resistance, while other research has found no effect on glucose levels. Until more is known, use melatonin cautiously in combination with antidiabetes drugs.
Severity Moderate Likelihood Possible Evidence B

Interaction has been documented in animal or in lab research, or the interaction has been documented in humans but is limited to case reports or conflicting clinical research exists.

Dr. Brian Staiger, PharmD, BCPS
Dr. Brian Staiger explains PharmD, Clinical Pharmacist

Here's the honest picture with melatonin and your Lantus (insulin glargine). The research is a bit of a mixed bag. Some studies show melatonin nudging blood sugar down, others show it pushing sugar up by making the body a little more resistant to insulin, and some show no real change at all. Because of that uncertainty, it's something to keep an eye on rather than panic about.

The main thing I'd watch for is low blood sugar (shakiness, sweating, dizziness, confusion, a fast heartbeat). Lantus is a long-acting insulin, so any shift in your numbers can show up overnight. I wouldn't change your dose on your own. If you want to use melatonin, just check your sugars a bit more closely at first and let your doctor or pharmacist know, so we can make sure things stay steady.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Cagnacci A, Arangino S, Renzi A, et al. Influence of melatonin administration on glucose tolerance and insulin sensitivity of postmenopausal women. Clin Endocrinol (Oxf) 2001;54:339-46.. PubMed
  2. Hussain, SA, Khadim, HM, Khalaf, BH, et al. Effects of melatonin and zinc on glycemic control in type 2 diabetic patients poorly controlled with metformin. Saudi Med J 2006;27:1483-8. DOI
  3. Kadhim, HM, Ismail, SH, Hussein, KI, et al. Effects of melatonin and zinc on lipid profile and renal function in type 2 diabetic patients poorly controlled with metformin. J Pineal Res 2006;41:189-93. PubMed
  4. Mutluay R. Elbeg S. Karakus R. et al. The Impact of Melatonin on Glucose Homeostasis. Turkish Journal of Endocrinology and Metabolism 2009;13:52-55.
  5. Doosti-Irani A, Ostadmohammadi V, Mirhosseini N et al. The effects of melatonin supplementation on glycemic control: A systematic review and meta-analysis of randomized controlled trials. Horm Metab Res. 2018;50(11):783-790. PubMed
  6. Farrokhian A, Tohidi M, Ahanchi NS, et al. Effect of bedtime melatonin administration in patients with type 2 diabetes: A triple-blind, placebo-controlled, randomized trial. Iran J Pharm Res. 2019;18(Suppl1):258-268.

What These Ratings Mean

Every interaction above is graded three ways — here’s the key to each label.

Severity how clinically significant the interaction is
Major

Clinically significant. Avoid the combination, or use only under close professional supervision.

Moderate

Usually worth avoiding or managing — may need monitoring, a dose change, or timing apart.

Minor

Generally not serious. Be aware of it and mention it to your pharmacist.

Likelihood how strong the evidence is that the interaction actually happens in people
  • LikelyWell-controlled human studies have demonstrated the likely existence of this interaction.
  • ProbableInteraction has not been documented in well-controlled studies, however, the interaction has been demonstrated in some small human studies or in controlled animal studies in conjunction with multiple case reports.
  • PossibleInteraction has been documented in animal or in lab research, or the interaction has been documented in humans but is limited to case reports or conflicting clinical research exists.
  • UnlikelyInteraction has been demonstrated in animal or in lab research but has been shown not to occur in humans.
Evidence the quality of the studies behind the rating (graded A–D)
  • AHigh-quality meta-analysis (quantitative systematic review).
  • BCase-control study.
  • CConsensus.
  • DAnecdotal evidence.

These ratings are for information only. Never start, stop, or otherwise change your therapy before speaking with your provider.

Keep it in perspective

Melatonin Also Interacts With Other Medications

Melatonin has 1,115 moderate, 345 minor known drug interactions in our database — the Insulin Glargine (rDNA) one above is one of them. If you take anything else, check it against the full list below.

Moderate 1,115 Minor 345 No known interaction 1,370 (incl. Insulin Glargine (rDNA))
Taking anything else?

Check Another of Your Medications Against Melatonin

Covers the 2,830 medications we’ve checked against Melatonin. Pick one to open its full report.

From our Q&A

Questions About Melatonin or Insulin Glargine (rDNA)

These are real questions from readers, answered by the pharmacists at HelloPharmacist — written by a person, not generated from a database. Each one covers Melatonin or Insulin Glargine (rDNA), not necessarily both, but if one is close to what you were about to ask it will usually go further than a database entry can:

Not quite your question? Ask our pharmacists directly — it is free, there is no account required, and answers usually come back within 24 hours.

Everything else you take

See Every Supplement That Interacts With Insulin Glargine (rDNA)

This page covers Melatonin only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Insulin Glargine (rDNA) page lists 242 supplements it has a documented interaction with, worst first, each one explained.

The most serious there right now: Chelation Therapy Products (major), Siberian Cocklebur (major), Acai (moderate), African Wild Potato (moderate) and Agaricus Mushroom (moderate).

By severity: 2 major · 211 moderate · 29 minor.

From our pharmacist’s overview on the Insulin Glargine (rDNA) page

“This page for insulin glargine (Lantus) runs to 242 ingredients, and it earns real care, because nearly everything on it moves blood sugar while your basal insulin dose stays fixed. Most add to the glucose-lowering effect and raise the odds of a low.”

Reviewed by 2 · Jul 18, 2026

Open the Insulin Glargine (rDNA) interaction page

One more smart check

Taking Melatonin as Part of a Dietary Supplement Product? Check It for Interactions

We hold 2,885 real supplement products containing Melatonin, each one broken down to its full ingredient list — and combination products often carry several ingredients besides Melatonin. Your product may carry other ingredients that interact with Insulin Glargine (rDNA) too, on top of Melatonin — and those would not show on this page. Find your product and we’ll check every ingredient on its label:

How much people look this up

Where Melatonin and Insulin Glargine (rDNA) Sit Against Everything Else

Out of every supplement and medication people look up on HelloPharmacist, here is where these two land this week — and which way each has been moving.

Supplement Melatonin
Top 5%

#55 of 1,452 supplements looked up here in the last 7 days

29 days ago today
Medication Insulin Glargine (rDNA)
Steady interest

#1,970 of 2,830 medications looked up here in the last 7 days

29 days ago today

Position among everything looked up on this site, not a measure of how commonly either one is used or how important it is. A supplement can climb this list because of a news story. It counts every request to the page, automated ones included, and nothing here identifies anyone.

Supplement

About Melatonin

What is Melatonin?

Melatonin
  • Trouble falling asleep (insomnia)
  • Jet lag
  • Delayed sleep phase syndrome
  • Non-24-hour sleep-wake disorder
  • Shift-work sleep problems
  • Sleep problems in some children with conditions like autism or ADHD

Melatonin is a hormone your body makes naturally to help control your sleep-wake cycle, and the supplement form is widely used to help with sleep timing problems and jet lag. The evidence is strongest for certain circadian (body-clock) disorders and is more mixed for everyday insomnia. It is generally well tolerated for short-term use, but talk with your pharmacist or doctor before starting, especially for children or during pregnancy.

Read the full Melatonin monograph & all interactions
Medication

About Insulin Glargine (rDNA origin) Injection

What Is Insulin Glargine (rDNA origin) Injection Used For?

Brand name: Lantus

Insulin glargine is used to improve glycemic control (blood sugar management) in adults and pediatric patients with type 1 diabetes mellitus, and in adults with type 2 diabetes mellitus. It is a long-acting basal insulin, meaning it works gradually over the course of the day to keep blood sugar steady.

Insulin glargine is not recommended for treating diabetic ketoacidosis (a serious complication where the blood becomes dangerously acidic).

See full Insulin Glargine (rDNA origin) Injection drug information
Keep checking

Other Drugs & Melatonin

Browse every other medication we’ve checked against Melatonin — both the ones with a known interaction and the ones without. Select any drug for the full detail.

0Major
1,115Moderate
345Minor
1,369No known interaction
1,115 Moderate 345 Minor 1,369 No interaction
Moderate

1,115 interactions

Showing 60 of 1,115 moderate interactions — see all 1,115 on the Melatonin page.

Minor

345 interactions

Showing 60 of 345 minor interactions — see all 345 on the Melatonin page.

No interaction 1,369 drugs checked — show the list

We also checked Melatonin against these medications and found no known interaction in our sources. Open any page to confirm.

Showing the 60 most looked-up of 1,369 medications checked with no known interaction — see the full Melatonin list.

See the full Melatonin interactions page
See every supplement checked against Insulin Glargine (rDNA), ranked by severity
Sources

Sources & How We Checked

Interaction details are evidence-graded and sourced from the Natural Medicines database. The medication overview comes from MedlinePlus.

Content is written and reviewed by licensed HelloPharmacist pharmacists. See our data sources and editorial standards for how this information is built and checked.

Parts of this content are provided by the Therapeutic Research Center, LLC.

DISCLAIMER: Currently this does not check for drug-drug interactions. This is not an all-inclusive comprehensive list of potential interactions and is for informational purposes only. Not all interactions are known or well-reported in the scientific literature, and new interactions are continually being reported. Input is needed from a qualified healthcare provider including a pharmacist before starting any therapy. Application of clinical judgment is necessary.

© 2021 Therapeutic Research Center, LLC

Keep exploring
Melatonin monograph › Uses, safety, and every drug interaction in one place Insulin Glargine (rDNA) supplement interactions › Every supplement checked against Insulin Glargine (rDNA), ranked by severity Insulin Glargine (rDNA origin) Injection drug information › The full plain-English guide to this medication Supplement interaction checker › Check any supplement or product against your medications Browse medications A–Z › Every drug we've checked against herbs & supplements Ask a pharmacist › Free, personal answer from our licensed team
Pharmacist Counseling Corner

Taking Melatonin and Insulin Glargine (rDNA) Together: Common Questions

Can you take Melatonin with Insulin Glargine (rDNA)?
There is a moderate interaction, so it may be acceptable with monitoring or timing changes — but check with your pharmacist first. Read the full details on this page and confirm with your pharmacist before combining them.
How serious is the Melatonin and Insulin Glargine (rDNA) interaction?
We rate it Moderate. This combination may require monitoring, a dose adjustment, or separating the times you take each one. Consult your pharmacist before using them together.

Written and reviewed by the HelloPharmacist editorial staff. Our editorial policy

Still Have a Question About Insulin Glargine (rDNA) and Melatonin?

Our pharmacists answer your medication & supplement questions — free.

Ask a pharmacist

This information is for education only and is not a substitute for professional medical advice. Always check with your pharmacist or doctor before starting, stopping, or combining supplements and medications.