Effect of L-carnitine supplementation on fertility outcomes among patients with polycystic ovary syndrome: a systematic review and dose-response meta-analysis of randomized clinical trials.

2025-07-15
Obstetrics & gynecology science 68(4)
- Ahmed Abu-Zaid
- Ghadeer Adel Alghamdi
- Alaa Saleh Alharbi
- Saeed Baradwan
- Saleh A K Saleh
- Heba M Adly
- Mooza M Alzayed
- Mohammed Abuzaid
- Raghad Sindi
- Mohannad Alsabban
- Osama Alomar

PubMed: 40436023
DOI: 10.5468/ogs.24272

Study Design

Type: Meta-Analysis
Sample size: n = 46
Population: patients with polycystic ovary syndrome (PCOS)
Methods: Systematic review and meta-analysis of randomized controlled trials; dose-response meta-analysis using a random-effects model; meta-regression

This systematic review and meta-analysis of randomized controlled trials (RCTs) assessed the effect of L-carnitine (LC) supplementation on the fertility outcomes of patients with polycystic ovary syndrome (PCOS). Online databases (Scopus, Web of Science, Cochrane Library, EMBASE, and PubMed) were searched to identify eligible RCTs published until March 2024. A dose-response meta-analysis was performed using a random-effects model. Meta-regression was also performed to investigate the source of heterogeneity based on the LC dose and duration of treatment. The pooled analysis included eight RCTs with 1,046 participants. The LC-treated group had significantly increased chemical and clinical pregnancy rates, ovulation rate, progesterone levels, number of preovulatory follicles >17 mm in diameter, and endometrial thickness compared to the untreated groups. The meta-analysis model indicated that LC supplementation did not change the serum levels of estrogen and testosterone; however, the dose-response meta-analysis indicated that prolonged LC intake significantly increased estrogen levels. LC supplementation has significant effects on fertility outcomes of women with PCOS. Additional large-scale longer RCTs are required to confirm the findings of this study.

Research Insights

L-Carnitine→Changed Estrogen Level
The meta-analysis model indicated that LC supplementation did not change the serum levels of estrogen and testosterone; however, the dose-response meta-analysis indicated that prolonged LC intake significantly increased estrogen levels.
Effect
Neutral
Effect size
Small
L-Carnitine→Changed Testosterone Level
The meta-analysis model indicated that LC supplementation did not change the serum levels of estrogen and testosterone; however, the dose-response meta-analysis indicated that prolonged LC intake significantly increased estrogen levels.
Effect
Neutral
Effect size
Small
L-Carnitine→Increased Chemical Pregnancy Rate
The LC-treated group had significantly increased chemical and clinical pregnancy rates, ovulation rate, progesterone levels, number of preovulatory follicles >17 mm in diameter, and endometrial thickness compared to the untreated groups.
Effect
Beneficial
Effect size
Moderate
L-Carnitine→Increased Clinical Pregnancy Rate
The LC-treated group had significantly increased chemical and clinical pregnancy rates, ovulation rate, progesterone levels, number of preovulatory follicles >17 mm in diameter, and endometrial thickness compared to the untreated groups.
Effect
Beneficial
Effect size
Moderate
L-Carnitine→Increased Endometrial Thickness
The LC-treated group had significantly increased chemical and clinical pregnancy rates, ovulation rate, progesterone levels, number of preovulatory follicles >17 mm in diameter, and endometrial thickness compared to the untreated groups.
Effect
Beneficial
Effect size
Moderate
L-Carnitine→Increased Estrogen Level
the dose-response meta-analysis indicated that prolonged LC intake significantly increased estrogen levels.
Effect
Beneficial
Effect size
Small
L-Carnitine→Increased Ovulation Rate
The LC-treated group had significantly increased chemical and clinical pregnancy rates, ovulation rate, progesterone levels, number of preovulatory follicles >17 mm in diameter, and endometrial thickness compared to the untreated groups.
Effect
Beneficial
Effect size
Moderate
L-Carnitine→Increased Preovulatory Follicle Count
The LC-treated group had significantly increased chemical and clinical pregnancy rates, ovulation rate, progesterone levels, number of preovulatory follicles >17 mm in diameter, and endometrial thickness compared to the untreated groups.
Effect
Beneficial
Effect size
Moderate
L-Carnitine→Increased Progesterone Level
The LC-treated group had significantly increased chemical and clinical pregnancy rates, ovulation rate, progesterone levels, number of preovulatory follicles >17 mm in diameter, and endometrial thickness compared to the untreated groups.
Effect
Beneficial
Effect size
Moderate