What happens at higher doses, what the Biogénique label actually warns about, and why a fishy smell is possible—but not the main safety issue for this formula.

A Fishy Smell Is Memorable. It Is Not the Whole Safety Story.

Search “L-carnitine side effects” and one unusual symptom dominates the conversation: fishy body odour. It is memorable, easy to repeat, and biologically plausible. But it can also distract from the more practical safety questions: dose, gastrointestinal tolerance, seizure risk in susceptible people, and—because this Biogénique formula also contains green tea extract—the label’s liver warnings.

The right way to answer the question is to separate three layers of evidence. First, what Biogénique’s current finished-product label actually says. Second, what Health Canada’s current ingredient monographs permit or require. Third, what outside research and clinical references report at doses that may be much higher than the Biogénique product provides.

Those layers are related, but they are not interchangeable. A side effect reported at 3 g/day of L-carnitine should not be rewritten as if it is expected from a 500 mg capsule. And a green-tea liver warning belongs to the green tea component of this finished formula—not to L-carnitine alone.

Sources: NIH ODS Carnitine Fact Sheet | Health Canada NPN 80086440

1. What Side Effects Are Actually Reported With L-Carnitine?

The most consistently described adverse effects from oral L-carnitine are gastrointestinal: nausea, vomiting, abdominal cramps and diarrhea. NIH’s Office of Dietary Supplements places the commonly cited cluster of GI effects and fishy body odour around supplemental intakes of approximately 3 g/day.

That dose context matters. Biogénique’s current label directs adults to take 1 capsule once or twice daily. Each capsule provides 500 mg of L-carnitine, so the labelled daily range is 500–1,000 mg/day. In other words, the labelled maximum is about one-third of the 3 g/day intake at which NIH highlights the classic high-dose side-effect cluster.

Sources: NIH ODS Consumer Carnitine | Biogénique L-Carnitine + Green Tea

2. Why Can L-Carnitine Cause a Fishy Body Odour?

The mechanism is tied to gut microbial metabolism. Some intestinal bacteria can metabolize unabsorbed L-carnitine into trimethylamine (TMA), a volatile compound with a characteristic fishy smell. TMA is normally absorbed and converted in the liver by the enzyme FMO3 into trimethylamine N-oxide (TMAO).

If TMA production is high relative to the body’s ability to process it—or if a person has an underlying impairment in TMA metabolism—TMA can accumulate and be released in breath, sweat and urine. That is the biological basis for the “fishy smell” discussion.

A published case report described fish-odour syndrome occurring during L-carnitine therapy and resolving after the supplement was stopped. Case reports can show that an event is possible; they do not tell us how often it occurs in typical supplement users or predict risk at Biogénique’s 500–1,000 mg/day labelled intake.

Sources: NIH ODS Health Professional Fact Sheet | L-Carnitine treatment and fish odor syndrome

3. Fishy Odour Is Not the Same Thing as TMAO Risk

TMA and TMAO are often collapsed into one story online, but they are not the same molecule and they answer different questions. TMA is the volatile compound responsible for the fishy smell. TMAO is the oxidized metabolite produced after TMA is processed in the liver.

Research has shown that oral L-carnitine can raise TMAO in some people, and the magnitude of the response varies with diet and the gut microbiome. Some observational studies associate higher TMAO levels with cardiovascular risk, but NIH explicitly notes that the implications of carnitine-related TMAO findings are not yet well understood. That is not a basis for telling consumers that a normal labelled dose of L-carnitine “causes heart disease.”

A systematic review of prolonged L-carnitine supplementation also concluded that more work is needed to understand the long-term cardiovascular meaning of elevated TMAO. The honest position is uncertainty—not alarmism and not dismissal.

Sources: NIH ODS Carnitine - TMAO discussion | Systematic review - L-carnitine supplementation

4. What Does the Current Biogénique Label Warn About?

For this specific finished product, the current label matters more than generic internet lists. Biogénique L-Carnitine + Green Tea is licensed under NPN 80086440. The current label in Biogénique’s product files provides 500 mg L-carnitine plus 50 mg green tea extract per capsule and directs adults to take 1 capsule once or twice daily with food, 2–4 hours before exercise.

• Consult a healthcare practitioner before use if you have kidney disease, a seizure disorder or a liver disorder.

• Consult a healthcare practitioner before use if you are pregnant or breastfeeding.

• Consult a healthcare practitioner before use if you have an iron deficiency.

• Stop use and consult a healthcare practitioner if symptoms of liver trouble develop, including yellowing of the skin/eyes, stomach pain, dark urine, sweating, nausea, unusual tiredness and/or loss of appetite.

• Keep out of reach of children.

Health Canada’s public licence record additionally identifies rare, unpredictable liver injury associated with green tea extract-containing products as the product’s known adverse reaction. That warning is important because this is not a single-ingredient L-carnitine supplement.

Sources: Health Canada NPN 80086440 | Health Canada green tea safety review

5. Green Tea Extract Changes the Safety Conversation

If this were pure L-carnitine, the main consumer safety discussion would focus on tolerance, dose and seizure precautions. But the Biogénique formula also contains green tea extract, so the finished-product risk profile includes green-tea-specific cautions.

Health Canada’s 2025 Green Tea Extract monograph directs green tea extract products to be taken with food and advises healthcare consultation for use beyond 12 weeks. It also carries liver-disorder and iron-deficiency cautions, and instructs users to stop if new symptoms consistent with liver injury appear.

This is why a side-effects article for a combination formula should not simply copy a generic L-carnitine list. The finished product is the unit the consumer actually takes.

Sources: Health Canada Green Tea Extract Monograph | Health Canada Summary Safety Review

6. Does L-Carnitine Increase Seizure Risk?

This is one of the areas where consumer summaries often become too absolute. Health Canada’s current L-carnitine monograph requires people with a seizure disorder to ask a healthcare practitioner before use. NIH also advises that high amounts may increase seizure risk in people with a seizure disorder.

That is a precaution—not proof that a healthy person without a seizure disorder will develop seizures from a standard supplement dose. The practical takeaway is narrower: if you have epilepsy, a history of seizures or use anticonvulsant medication, do not self-experiment with escalating doses.

Sources: Health Canada L-Carnitine Monograph | NIH ODS Carnitine

7. What Does Lot 241027 Testing Tell Us?

Side-effect research and a Certificate of Analysis answer different questions. Clinical literature describes possible biological effects in people. A COA shows whether a tested finished-product lot met the listed manufacturing and quality specifications.

The tested lot met the listed specifications. Biogénique’s 3X PUR™ framework organizes these lot results as Pureté, Qualité and Performance; 3X PUR™ is Biogénique’s framework for interpreting testing and is not a laboratory-issued certification.

Sources: Biogénique Quality Control / COAs

8. When Should You Stop and Get Advice?

• A new fishy body odour appears and persists despite stopping or reducing supplemental L-carnitine.

• You develop repeated vomiting, significant diarrhea or abdominal pain.

• You have a seizure or a meaningful change in seizure control.

• You develop yellowing of the skin or eyes, dark urine, unusual fatigue, loss of appetite or persistent nausea.

• You are taking prescription medication and are unsure whether the supplement fits safely with your regimen.

• You are pregnant, breastfeeding, have kidney/liver disease or iron deficiency, or are being evaluated for any of these.

Do not treat a persistent unusual body odour as something to simply mask with deodorant if it began after a supplement change. Dose reduction or discontinuation may resolve a supplement-related cause, but persistent odour can also have causes unrelated to L-carnitine and deserves proper evaluation.

9. A Practical Decision Framework

Frequently Asked Questions

Can L-carnitine make you smell like fish?

It can, particularly at higher supplemental doses. NIH highlights fishy body odour around approximately 3 g/day. Biogénique’s labelled maximum is 1 g/day, so do not assume the high-dose effect is expected at the product’s labelled dose.

Why does L-carnitine cause fishy body odour?

Gut bacteria can convert L-carnitine to trimethylamine (TMA), a volatile compound with a fishy smell. The liver normally converts TMA to TMAO. Individual microbiome and metabolism differences affect how much TMA is produced and cleared.

Is the fishy smell dangerous?

The smell itself does not prove toxicity. But a new persistent odour after increasing L-carnitine is a reason to stop or reduce the supplement and reassess. Persistent odour can also have other causes.

Does Biogénique L-Carnitine + Green Tea cause diarrhea?

Diarrhea is a known high-dose L-carnitine effect in the broader literature, but it is not listed as a known adverse reaction on this finished product’s current Health Canada record. Individual tolerance still varies.

Can L-carnitine cause liver damage?

The current Biogénique product’s liver warning is driven by its green tea extract component. Health Canada identifies rare, unpredictable liver injury with green tea extract-containing products. Do not rewrite that warning as proof that L-carnitine itself causes liver injury.

What about TMAO?

L-carnitine can increase TMAO in some people. Higher TMAO has been associated with cardiovascular risk in observational research, but the clinical meaning of supplement-induced TMAO changes is still uncertain. More research is needed.

Is 500 mg of L-carnitine a high dose?

No. The current Health Canada L-carnitine monograph uses gram-level ranges for several ingredient claims. Biogénique provides 500 mg per capsule and a labelled maximum of 1,000 mg/day.

Should I take it with food?

Yes. Biogénique’s current label says to take 1 capsule once or twice daily with food, and 2–4 hours before exercise.

Can I take more if I do not feel anything?

No. Lack of a noticeable sensation is not evidence that the dose is too low. Stay within the label unless a qualified healthcare professional gives you a different plan.

Is fishy odour listed on Biogénique’s label?

No. The current product label does not list fishy body odour as a known adverse reaction. The body-odour discussion in this article comes from external L-carnitine safety literature and is clearly separated from the licensed Biogénique product claims.

Bottom Line

L-carnitine’s “fishy smell” side effect is real enough to take seriously, but it is usually discussed in the context of much higher supplemental intakes than the Biogénique product provides. NIH highlights the classic nausea, vomiting, cramps, diarrhea and fishy body odour cluster at around 3 g/day. Biogénique’s labelled maximum is 1 g/day.

That does not make the formula risk-free. This is a combination product. Its current Canadian label carries kidney, seizure, liver, pregnancy/breastfeeding and iron-deficiency cautions, and Health Canada identifies rare, unpredictable liver injury associated with green tea extract-containing products.

The source of truth is therefore not a viral side-effect list. It is the current NPN, the current finished-product label, the matching lot COA, and external literature interpreted at the dose and formulation actually studied.

Related Biogénique Resources

• L-Carnitine + Green Tea - Product Details

• Quality Control / Certificates of Analysis

• VitaQuiz / Find My Formula

• Research & Innovation

Evidence & Compliance Note

Biogénique-specific claims in this article are based on the current finished-product label and Health Canada licence for NPN 80086440, together with matching lot 241027 quality data. External information about fishy body odour, gastrointestinal effects, TMA/TMAO and high-dose safety comes from outside research and is not presented as an authorized Biogénique product claim. Dose-dependent adverse effects reported around 3 g/day are not assumed to occur at Biogénique’s labelled 500–1,000 mg/day intake.

Data-reconciliation note: Health Canada’s public NPN record currently lists hypromellose, magnesium stearate, microcrystalline cellulose and silicon dioxide as non-medicinal ingredients, while the current Biogénique lot 241027 label and matching COA list hypromellose and magnesium stearate. This discrepancy is documented rather than silently reconciled. It does not affect the medicinal-ingredient dose or the side-effect conclusions in this article, but should be reviewed in the regulatory/product records.

References

1. Biogénique. L-Carnitine + Green Tea product page. NPN 80086440. Source

2. Health Canada. Licensed Natural Health Products Database: NPN 80086440. Source

3. Health Canada. Natural Health Product Monograph: L-Carnitine. July 25, 2025. Source

4. Health Canada. Natural Health Product Monograph: Green Tea Extract. July 25, 2025. Source

5. Health Canada. Summary Safety Review - Green tea extract-containing natural health products and liver injury. Source

6. NIH Office of Dietary Supplements. Carnitine - Health Professional Fact Sheet. Source

7. NIH Office of Dietary Supplements. Carnitine - Consumer Fact Sheet. Source

8. L-Carnitine treatment and fish odor syndrome: an unwaited adverse effect. Revue Neurologique. 2011. Source

9. The bright and the dark sides of L-carnitine supplementation: a systematic review. Source

10. Biogénique Certificate of Analysis, L-Carnitine + Green Tea, lot 241027. Internal product file; manufactured Oct 2024; expiry Sep 2027. Source

Disclaimer

This article is for consumer education only and is not medical advice. Natural health products are not substitutes for diagnosis or treatment. Follow the current product label. If you are pregnant or breastfeeding, take prescription medications, have kidney or liver disease, have a seizure disorder, have iron deficiency, or develop persistent or concerning symptoms, speak with a qualified healthcare professional.