J Endocrinol Metab

Journal of Endocrinology and Metabolism, ISSN 1923-2861 print, 1923-287X online, Open Access

Article copyright, the authors; Journal compilation copyright, J Endocrinol Metab and Elmer Press Inc

Journal website https://jem.elmerpub.com

Original Article

Volume 16, Number 2, April 2026, pages 109-117

Impact of L-Carnitine on Reproductive Outcomes in Women With Polycystic Ovarian Syndrome: A Systematic Review and Meta-Analysis of Randomized Controlled Trials

↓ Figure 1. PRISMA flow diagram illustrating the systematic literature search and study selection process, including the number of records identified, screened, assessed for eligibility, and finally included in the meta-analysis.

↓ Figure 2. Risk of bias summary for the included randomized controlled trials assessed using the Cochrane Risk of Bias tool (RoB 1), displaying judgments across six domains for each included study.

↓ Figure 3. Forest plot of ovulation rate in women with PCOS receiving L-carnitine supplementation versus control during controlled ovarian stimulation.

↓ Figure 4. Forest plot of clinical pregnancy rate in women with PCOS receiving L-carnitine supplementation versus control during controlled ovarian stimulation.

↓ Figure 5. Forest plot of endometrial thickness in women with PCOS receiving L-carnitine supplementation versus control during controlled ovarian stimulation.

↓ Figure 6. Forest plot of number of mature follicles in women with PCOS receiving L-carnitine supplementation versus control during controlled ovarian stimulation.

↓ **Table 1.** Characteristics of the Included Studies
Study ID	Study location	Study arms	Sample size	Maternal age (years)	BMI	Duration of infertility (years)	Type of infertility, n (%)	Interventions
BMI: body mass index; CC: clomiphene citrate; GnRH: gonadotropin-releasing hormone; LC: L-carnitine; NA: not available.
Hafezi et al, 2024 [14]	Iran	LC group	47	29.8 ± 4	27.4 ± 5.2	6.8 ± 3.9	40 (85)	7 (15)	Three tablets of L-carnitine (1,000 mg) daily plus GnRH antagonist protocol.
		Control group	50	30.4 ± 4.3	27.4 ± 3.7	6.5 ± 4	39 (78)	11 (22)	Placebo plus GnRH antagonist protocol.
Chaleshtori et al, 2022 [19]	Iran	LC group	74	30.29 ± 2.2	30.85 ± 1.93	2.3 ± 1.6	74 (100)	0 (0)	150 mg/day oral CC plus 3 g oral L-carnitine daily.
		Control group	74	31.29 ± 4.7	31.45 ± 5.71	2.14 ± 1.9	55 (74)	19 (26)	150 mg/day oral CC plus placebo.
Sheida et al, 2023 [20]	Iran	LC group	41	30 ± 5.01	28.06 ± 3.38	5.92 ± 2.94	35 (85)	6 (15)	L-carnitine (3,000 mg) daily plus GnRH antagonist protocol.
		Control group	39	31.57 ± 4.7	28.22 ± 3.33	5.95 ± 3.95	35 (90)	4 (10)	Placebo plus GnRH antagonist protocol.
Kortam et al, 2020 [18]	Egypt	LC group	47	25.2 ± 3.9	30 ± 5.2	2.35 ± 1.5	34 (72)	13 (28)	Oral CC (50 mg tablet, two times per day) plus oral L-carnitine supplementation (1 g tablet, three times per day).
		Control group	47	25.8 ± 2.6	30.4 ± 3	2.2 ± 0.9	35 (74)	12 (26)	Oral CC (50 mg tablet, two times per day) plus placebo.
Gharib, 2019 [13]	Egypt	LC group	20	24.65 ± 2.1	28.25 ± 1.8	2.8 ± 0.83	NA	NA	Letrozole (2.5 mg tablets) plus L-carnitine (2 g/day)
		Control group	20	24.15 ± 2.45	27.49 ± 2.3	3.1 ± 1.09	NA	NA	Letrozole (2.5 mg tablets) plus placebo.
Abd-Elfattah et al, 2019 [17]	Egypt	LC group	25	26.12 ± 3.28	31.22 ± 2.56	NA	NA	NA	100–150 mg/day oral CC plus L-carnitine (3 g daily)
		Control group	25	25.64 ± 2.63	31.79 ± 2.72	NA	NA	NA	100–150 mg/day oral CC plus placebo.

↓ Table 1. Characteristics of the Included Studies

Study ID

Study location

Study arms

Sample size

Maternal age (years)

BMI

Duration of infertility (years)

Type of infertility, n (%)

Interventions

Primary

Secondary

BMI: body mass index; CC: clomiphene citrate; GnRH: gonadotropin-releasing hormone; LC: L-carnitine; NA: not available.

Hafezi et al, 2024 [14]

Iran

LC group

29.8 ± 4

27.4 ± 5.2

6.8 ± 3.9

40 (85)

7 (15)

Three tablets of L-carnitine (1,000 mg) daily plus GnRH antagonist protocol.

Control group

30.4 ± 4.3

27.4 ± 3.7

6.5 ± 4

39 (78)

11 (22)

Placebo plus GnRH antagonist protocol.

Chaleshtori et al, 2022 [19]

Iran

LC group

30.29 ± 2.2

30.85 ± 1.93

2.3 ± 1.6

74 (100)

0 (0)

150 mg/day oral CC plus 3 g oral L-carnitine daily.

Control group

31.29 ± 4.7

31.45 ± 5.71

2.14 ± 1.9

55 (74)

19 (26)

150 mg/day oral CC plus placebo.

Sheida et al, 2023 [20]

Iran

LC group

30 ± 5.01

28.06 ± 3.38

5.92 ± 2.94

35 (85)

6 (15)

L-carnitine (3,000 mg) daily plus GnRH antagonist protocol.

Control group

31.57 ± 4.7

28.22 ± 3.33

5.95 ± 3.95

35 (90)

4 (10)

Placebo plus GnRH antagonist protocol.

Kortam et al, 2020 [18]

Egypt

LC group

25.2 ± 3.9

30 ± 5.2

2.35 ± 1.5

34 (72)

13 (28)

Oral CC (50 mg tablet, two times per day) plus oral L-carnitine supplementation (1 g tablet, three times per day).

Control group

25.8 ± 2.6

30.4 ± 3

2.2 ± 0.9

35 (74)

12 (26)

Oral CC (50 mg tablet, two times per day) plus placebo.

Gharib, 2019 [13]

Egypt

LC group

24.65 ± 2.1

28.25 ± 1.8

2.8 ± 0.83

Letrozole (2.5 mg tablets) plus L-carnitine (2 g/day)

Control group

24.15 ± 2.45

27.49 ± 2.3

3.1 ± 1.09

Letrozole (2.5 mg tablets) plus placebo.

Abd-Elfattah et al, 2019 [17]

Egypt

LC group

26.12 ± 3.28

31.22 ± 2.56

100–150 mg/day oral CC plus L-carnitine (3 g daily)

Control group

25.64 ± 2.63

31.79 ± 2.72

100–150 mg/day oral CC plus placebo.