Yu Sleep Side Effects: What the Sources Say About Each Ingredient

If you are weighing Yu Sleep, the safety question is a fair one. Here is the honest answer: we cannot say what side effects the product itself causes. A PubMed search for “Yu Sleep” in titles and abstracts on September 19, 2026 returned no results, so no study of the finished product turned up.

What does exist is research and official guidance on its ingredients. This guide sets out what NIH and published reviews say about each one, where the label lets us put a ceiling on the amount, and where we have not looked. It is not medical advice.

The Short Answer

• We found no study of Yu Sleep itself. Everything below is about its ingredients, at the amounts those sources describe.
• Melatonin and 5-HTP carry the most documented cautions. For melatonin, people with epilepsy and people taking blood thinners should be under medical supervision. For 5-HTP, an excess may lead to serotonin syndrome, which the review we read links to antidepressant medications.
• Seven of the ten ingredients share one 637 mg blend with no amounts listed, so for those we can only give ceilings.
• Vitamin B6 is disclosed at 0.5 mg, far below the upper limit NIH lists, and NIH says riboflavin (vitamin B2, also 0.5 mg) has not been shown to cause any harm.
• We have not reviewed the safety of apigenin, GABA, red tart cherry or the other ingredients.

What the Label Lets Us Say About Amounts

The Supplement Facts panel gives amounts for melatonin (0.9 mg), vitamin B2 (0.5 mg) and vitamin B6 (0.5 mg). The other seven ingredients share a 637 mg blend. Our ingredients guide lists all ten together with what independent research says about each. US labeling rules require the ingredients inside a blend to be listed in descending order by weight (21 CFR 101.36(c)(2)). If this label follows that rule, each ingredient can weigh no more than the blend’s 637 mg divided by its position in the list, because everything listed before it weighs at least as much.

These are ceilings, not amounts. The real figures could be much lower. Red tart cherry juice concentrate is listed first, so the rule gives it no ceiling below the blend’s 637 mg. The elemental magnesium figure assumes the glycinate is about 14% magnesium by weight. Our Yu Sleep review shows the label and explains the arithmetic.

What the Sources Say, Ingredient by Ingredient

Melatonin: 0.9 mg per serving, disclosed

The National Center for Complementary and Integrative Health (NCCIH) says short-term use of melatonin supplements appears to be safe for most people, and that information on long-term safety is lacking. The mild side effects reported in short-term studies of adults, surgical patients and critically ill patients included headache, dizziness, nausea and sleepiness. It adds that there may be a risk of allergic reactions.

NCCIH says people with epilepsy and people taking blood thinners need to be under medical supervision if they take melatonin, and that anyone taking medicine should consult a healthcare provider first. There has been a lack of research on melatonin in pregnant or breastfeeding women. For children, it says parents should speak with a provider first. Reported effects in children have usually been mild: drowsiness, more bedwetting or evening urination, headache, dizziness and agitation. Because melatonin is a hormone, NCCIH says it is possible that it could affect hormonal development, but that this is not known for sure.

NCCIH also notes that some melatonin supplements may not contain what the label says (NCCIH, Melatonin: What You Need To Know). That is why the label-versus-bottle question in our review matters.

5-HTP: amount not disclosed, at most about 127 mg

5-HTP is a precursor of serotonin. A 2020 review of its toxicology, written by a single author at the University of Turin, says it may cause dose-dependent gastrointestinal problems, with nausea and vomiting reported at doses above 100 mg. It says an excess of 5-HTP may lead to serotonin syndrome, which it describes as resulting from antidepressant medications and as marked by altered mental status, autonomic dysfunction and neuromuscular abnormalities. It also says excessive use was associated with severe side effects, including behavioral disturbances and abnormal mental function, and that relatively few adverse effects were associated with 5-HTP in early studies in depressed patients (Maffei, International Journal of Molecular Sciences, 2020).

The label does not give the amount. If the ordering rule holds, it is at most about 127 mg, which is above the 100 mg at which the review reports nausea and vomiting. It could be far lower. We cannot tell you which side of that line a serving falls on. If you take an antidepressant or any other medication that acts on serotonin, ask your prescriber before you add a 5-HTP product.

The review also records a quality problem from the past. Tryptophan supplements were pulled in 1989 after an outbreak of eosinophilia-myalgia syndrome, a rare and sometimes fatal condition traced to contaminated synthetic tryptophan from a single manufacturer. The review says toxic impurities in tryptophan and in 5-HTP preparations have caused cases, and it records a disagreement over how much trace impurities found in some commercial 5-HTP samples matter. That is a history of manufacturing quality, not a finding about this product. The label names the source as Griffonia seed extract and says nothing about how the 5-HTP is tested.

Magnesium glycinate: amount not disclosed, at most about 45 mg of elemental magnesium

The NIH Office of Dietary Supplements (ODS) sets an upper limit of 350 mg a day for adults for magnesium from supplements and medications. It says high intakes from those sources can cause diarrhea, nausea and abdominal cramping, and that in healthy people the kidneys can excrete any excess in the urine. If the ordering rule holds, a serving of Yu Sleep holds at most about 45 mg of elemental magnesium, about an eighth of that limit. Magnesium from other supplements and medicines counts toward the same limit.

ODS lists medicines that interact with magnesium. Bisphosphonates for osteoporosis and some antibiotics may not be absorbed if taken too close to a magnesium supplement. Diuretics can raise or lower magnesium loss, depending on the type. Drugs for acid reflux or peptic ulcers can lower blood magnesium when taken for a long time (NIH ODS, Magnesium: Fact Sheet for Consumers).

Vitamins B6 and B2: 0.5 mg each, disclosed

ODS says taking high amounts of vitamin B6 from supplements for a year or longer can cause severe nerve damage, and it lists an upper limit for adults of 100 mg a day from all sources. It notes that the European Food Safety Authority set a lower limit in 2023, 12 mg a day for adults. At 0.5 mg per serving, Yu Sleep supplies about 0.5% of the NIH limit and about 4% of the European one, before counting any other B6 you take. ODS says B6 supplements can interact with cycloserine, an antibiotic used for tuberculosis, and that certain epilepsy drugs and theophylline can lower B6 levels (NIH ODS, Vitamin B6: Fact Sheet for Consumers).

For vitamin B2, ODS says riboflavin has not been shown to cause any harm (NIH ODS, Riboflavin: Fact Sheet for Consumers).

L-theanine: amount not disclosed, at most about 106 mg

A 2015 review says L-theanine “does not induce daytime drowsiness” and gives a no-observable-adverse-effect level above 2000 mg per kg of body weight a day, a toxicology figure and not a dose to take. The sleep studies it summarizes point to 200 mg before bed. If the ordering rule holds, the most Yu Sleep can hold is about 106 mg (Rao, Ozeki and Juneja, Journal of the American College of Nutrition, 2015).

One caution about that source: all three authors are listed as working for Taiyo Kagaku Co. Ltd., a company that makes L-theanine.

GABA: amount not disclosed, at most about 91 mg

We have not reviewed the safety of oral GABA. The systematic review we rely on in our Yu Sleep review looks at stress and sleep outcomes, and its abstract does not report safety findings.

Lemon balm: amount not disclosed, at most about 159 mg

A 2024 review of lemon balm and psychological well-being says the human trials it covers used daily doses from 80 mg to 5000 mg, for up to 8 weeks, as capsules, tablets and tea, and that they were well tolerated. It says adverse effects above 5000 mg a day, or beyond 56 days, are unclear. The trials used other preparations, so the comparison with this product’s extract is loose, though the ceiling of about 159 mg falls inside that range. The review was funded by Givaudan France Naturals, and two of its authors were employed there (Mathews et al., Nutrients, 2024).

Apigenin, red tart cherry and the other ingredients

We have not reviewed the safety of apigenin or of red tart cherry juice concentrate, and the label gives no amount for either. If you have an allergy or an intolerance, the label’s “Other ingredients” line is the place to look. It lists distilled water, glycerin, medium invert syrup, citric acid, erythritol, sodium citrate dihydrate, natural flavors, gum arabic, xanthan gum and potassium sorbate, and it repeats magnesium glycinate, apigenin and lemon balm extract. “Natural flavors” does not say what the flavors are.

Who Should Ask a Healthcare Provider First

The sources above point to the same groups.

• People who take any medication. NCCIH says so for melatonin. The sources name specific cases: antidepressants and other medicines that act on serotonin (5-HTP), blood thinners and epilepsy medicines (melatonin), bisphosphonates, antibiotics, diuretics and acid-reflux drugs (magnesium), and cycloserine, certain epilepsy drugs and theophylline (vitamin B6).
• People who are pregnant or breastfeeding. NCCIH says it is especially important to see a provider before taking any medicine or supplement, including melatonin.
• Parents considering it for a child. NCCIH says to speak with a provider first.
• People with epilepsy or another medical condition, and anyone about to have surgery. NCCIH says some dietary supplements may interact with medicines or pose risks if you have medical problems or are going to have surgery.

What We Do Not Know

• How much of seven ingredients a serving contains.
• Whether the amounts in the bottle match the label. We have not checked one against a physical bottle.
• How the ingredients behave together. The sources above look at one ingredient at a time, and this guide cites no study of the combination.
• What happens with long-term use. NCCIH says information on the long-term safety of melatonin is lacking, and the lemon balm review calls effects beyond 56 days unclear.
• The safety of apigenin, GABA and red tart cherry, which we have not reviewed.

If You Have a Reaction

Contact a healthcare provider, and get emergency care if the reaction is severe. In the United States, the FDA’s MedWatch program takes reports of serious reactions and product quality problems with dietary supplements, including from consumers. Its toll-free line is 1-888-INFO-FDA (1-888-463-6332); press 2 to report to MedWatch.

Questions

Does Yu Sleep have side effects?

We cannot say for the product, because we found no study of it. For its ingredients, the sources we read report mostly mild effects at the amounts studied: headache, dizziness, nausea and sleepiness with melatonin, and stomach upset with 5-HTP at higher doses and with magnesium at high supplement doses. The same sources name groups who should ask a provider first, listed above.

Can I take Yu Sleep with antidepressants?

We cannot tell you. The 5-HTP review links serotonin syndrome to antidepressant medications, and the label does not say how much 5-HTP a serving holds. Ask the person who prescribes your medication.

Is Yu Sleep safe during pregnancy?

We cannot say that it is. NCCIH reports a lack of research on melatonin in pregnant or breastfeeding women, and we have not reviewed several of the other ingredients. Ask your provider before using it.

Can I take it every night?

The sources do not settle this. NCCIH says information on the long-term safety of melatonin is lacking, the lemon balm review calls effects beyond 56 days unclear, and this guide cites no study of the product itself.

Bottom Line

In the sources we read, the effects reported at the amounts studied were mostly mild. The cautions that matter most are the medication interactions around 5-HTP and melatonin, and the fact that seven amounts are hidden in a blend, so nobody can tell you how much of them you would take. If you take medication, are pregnant or breastfeeding, or have a medical condition, talk to a healthcare provider first. Nothing here is a guarantee.

Sources Cited in This Guide

1. National Center for Complementary and Integrative Health, NIH. “Melatonin: What You Need To Know.” Read September 19, 2026. NCCIH
2. Maffei ME. “5-Hydroxytryptophan (5-HTP): Natural Occurrence, Analysis, Biosynthesis, Biotechnology, Physiology and Toxicology.” Int J Mol Sci. 2020. PMID 33375373
3. NIH Office of Dietary Supplements. “Magnesium: Fact Sheet for Consumers.” Updated March 22, 2021. Read September 19, 2026. ODS
4. NIH Office of Dietary Supplements. “Vitamin B6: Fact Sheet for Consumers.” Updated June 16, 2023. Read September 19, 2026. ODS
5. NIH Office of Dietary Supplements. “Riboflavin: Fact Sheet for Consumers.” Updated May 11, 2022. Read September 19, 2026. ODS
6. Rao TP, Ozeki M, Juneja LR. “In Search of a Safe Natural Sleep Aid.” J Am Coll Nutr. 2015. PMID 25759004
7. Hepsomali P, et al. “Effects of Oral Gamma-Aminobutyric Acid (GABA) Administration on Stress and Sleep in Humans: A Systematic Review.” Front Neurosci. 2020. PMID 33041752
8. Mathews IM, et al. “Clinical Efficacy and Tolerability of Lemon Balm (Melissa officinalis L.) in Psychological Well-Being: A Review.” Nutrients. 2024. PMID 39458539
9. U.S. Food and Drug Administration. “Reporting Serious Problems to FDA” (MedWatch). Read September 19, 2026. FDA
10. 21 CFR 101.36(c)(2). Read September 19, 2026. eCFR
11. PubMed search for “yu sleep” in titles and abstracts, run September 19, 2026: 0 results. Repeat the search

This guide is for information and is not medical advice. Talk to a healthcare provider about medication, pregnancy, medical conditions and persistent sleep problems.