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Lemon balm side effects: is it safe?

Written by the Full Measure editorial team, which sells supplements. Approved for publication by the Full Measure owners. Updated .

Drafted with AI assistance from the sources listed below. How we write these

Quick answer

Lemon balm is generally well tolerated. NIH's lactation database lists occasional nausea, vomiting, stomach ache, dizziness and wheezing, and a 900 mg single dose lowered alertness in one study. No official source names a medicine interaction, but test tube work raises a thyroid question. Ask first if pregnant, breastfeeding or taking thyroid medicine.1,2,3

Key facts

  • In a three-week trial, mild stomach upset was as common with placebo as with lemon balm.4
  • The longest safety record is a 96-week trial in 323 older adults.5
  • A single dose did not change liver, kidney or blood count tests in 11 healthy adults.6
  • No case of liver harm from lemon balm is recorded in LiverTox.7

Side effects reported

Lemon balm is generally well tolerated. Nausea, vomiting, stomach pain, dizziness and wheezing have been reported occasionally.1

In a three-week trial, mild stomach upset was about as common with lemon balm (4 of 52 people) as with placebo (5 of 48).4

Other trials reported few problems. The two-week crossover sleep trial found no side effects linked to the extract, and the authors of the 15-day open trial judged 600 mg a day safe over that period.8,9

Drowsiness and alertness

In single-dose studies, the highest dose of one extract lowered alertness for several hours, and some doses slowed timed memory tasks.2,10

In those studies, 900 mg of one extract lowered alertness at every point measured over six hours, and 600 mg lowered alertness during a stressful test while raising calm. Do not drive or use machinery if you feel drowsy, and ask before combining lemon balm with sedatives or sleep medicines.2,11

The thyroid question

In test tube studies, freeze-dried lemon balm extract blocked thyroid stimulating hormone (TSH) from binding to human thyroid cell membranes. We found no study testing whether this happens in people taking a supplement.3

That work, from the 1980s, applied freeze-dried water extracts to thyroid tissue in the lab. No official source we could find lists a thyroid medicine interaction, and we found no study in people. If you have a thyroid condition or take levothyroxine or another thyroid medicine, ask your doctor before using lemon balm.3

Medicines

No official source we could find, including NIH's liver and lactation databases, names a specific medicine that interacts with lemon balm. That does not show any combination is safe. Tell your pharmacist about every supplement you take, and ask first if you take sedatives, sleep medicines or thyroid medicine.1,7

Pregnancy and breastfeeding

The official sources we use give no safety information on lemon balm in pregnancy, so ask your doctor or midwife first. NIH's lactation database has no data on lemon balm passing into breast milk or on its use alone by nursing mothers, though it rates the tiny amounts expected in milk as probably harmless with usual doses.1

Lemon balm is also said to raise milk supply. The same database calls the evidence for that weak.1

Liver and lab tests

LiverTox, NIH's database of liver injury from medicines and supplements, says lemon balm extracts have not been linked to raised liver enzymes or to liver injury.7

In the 96-week trial, vital signs and physical and neurological checks did not differ between the extract and placebo groups.5

What's in ours

What’s in ours

  • Sleep: Lemon Balm Extract, 100 mg per serving, from the label

Questions people ask

Is lemon balm safe to eat?

As a food flavoring, yes: FDA lists lemon balm as generally recognized as safe for that use. Supplement doses are a separate question, covered above.1

Is lemon balm safe to take daily?

The longest daily study ran 96 weeks in older adults and found no differences from placebo in physical checks. Most other trials lasted three weeks or less, so long-term daily use in younger adults has had little study.4,5,8,9

Can kids take lemon balm?

No children's dose of lemon balm alone has been studied. Infants have been given it only in mixtures with other herbs. Ask a pediatrician first.1

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Sources

  1. Lemon Balm. In: Drugs and Lactation Database (LactMed). Bethesda (MD): National Institute of Child Health and Human Development; 2006 onward. Updated March 15, 2026. Read through PubMed. Opened 2026-10-07.
  2. Kennedy DO, Scholey AB, Tildesley NT, Perry EK, Wesnes KA. Modulation of mood and cognitive performance following acute administration of Melissa officinalis (lemon balm). Pharmacol Biochem Behav. 2002;72(4):953-964. Opened 2026-10-07.
  3. Auf'mkolk M, Ingbar JC, Amir SM, et al. Inhibition by certain plant extracts of the binding and adenylate cyclase stimulatory effect of bovine thyrotropin in human thyroid membranes. Endocrinology. 1984;115(2):527-534. Opened 2026-10-07.
  4. Bano A, Hepsomali P, Rabbani F, et al. The possible calming effect of subchronic supplementation of a standardised phospholipid carrier-based Melissa officinalis L. extract in healthy adults with emotional distress and poor sleep conditions: results from a prospective, randomised, double-blinded, placebo-controlled clinical trial. Front Pharmacol. 2023;14:1250560. Opened 2026-10-07.
  5. Noguchi-Shinohara M, Hamaguchi T, Sakai K, et al. Effects of Melissa officinalis Extract Containing Rosmarinic Acid on Cognition in Older Adults Without Dementia: A Randomized Controlled Trial. J Alzheimers Dis. 2023;91(2):805-814. Opened 2026-10-07.
  6. Noguchi-Shinohara M, Ono K, Hamaguchi T, et al. Pharmacokinetics, Safety and Tolerability of Melissa officinalis Extract which Contained Rosmarinic Acid in Healthy Individuals: A Randomized Controlled Trial. PLoS One. 2015;10(5):e0126422. Opened 2026-10-07.
  7. Lemon Balm. In: LiverTox: Clinical and Research Information on Drug-Induced Liver Injury. Bethesda (MD): National Institute of Diabetes and Digestive and Kidney Diseases; 2012 onward. Updated February 10, 2024. Summary read through PubMed. Opened 2026-10-07.
  8. Di Pierro F, Sisti D, Rocchi M, et al. Effects of Melissa officinalis Phytosome on Sleep Quality: Results of a Prospective, Double-Blind, Placebo-Controlled, and Cross-Over Study. Nutrients. 2024;16(23):4199. Opened 2026-10-07.
  9. Cases J, Ibarra A, Feuillère N, Roller M, Sukkar SG. Pilot trial of Melissa officinalis L. leaf extract in the treatment of volunteers suffering from mild-to-moderate anxiety disorders and sleep disturbances. Med J Nutrition Metab. 2011;4(3):211-218. Opened 2026-10-07.
  10. Kennedy DO, Wake G, Savelev S, et al. Modulation of mood and cognitive performance following acute administration of single doses of Melissa officinalis (lemon balm) with human CNS nicotinic and muscarinic receptor-binding properties. Neuropsychopharmacology. 2003;28(10):1871-1881. Opened 2026-10-07.
  11. Kennedy DO, Little W, Scholey AB. Attenuation of laboratory-induced stress in humans after acute administration of Melissa officinalis (lemon balm). Psychosom Med. 2004;66(4):607-613. Opened 2026-10-07.

This page is information, not medical advice. Talk to your doctor or pharmacist about your own situation.