The goal of this clinical trial is to learn if Vitamin C works to improve ovarian reserve in women with ovarian aging. It will also learn about the safety of Vitamin C. The main questions it aims to answer are:

• Does Vitamin C supplementation improve the ovarian reserve prediction score?
• What medical problems do participants have when taking Vitamin C supplementation?

Researchers will compare Vitamin C to a placebo (a look-alike substance that contains no drug) to see if drug Vitamin C works to improve ovarian reserve in women with ovarian aging. Participants will:

• Take Vitamin C or a placebo every day for 12 months
• Visit the clinic once every 4 weeks for follow-up and drug distribution.
• Return the Vitamin C box at each visit.
• Report any adverse effects of treatment to the doctor.
• Fill out a questionnaire at each visit.
• After 6 months and 12 months of intervention, take blood test and ultrasonic examination.

Inclusion Criteria:

• Regularity of menstruation changed for less than one year.
• 10U/L≤ FSH<25 U/L in two tests more than 4weeks aprt.
• AMH < 1.1 ng/mL.
• Bilateral ovarian AFC <7.
• Signed informed consent and can participate in regular follow-ups.

Exclusion Criteria:

• Ovarian aging caused by TUNER (X deletion) syndrome or gene mutation.
• Ovarian aging caused by ovarian surgery or chemotherapy.
• Patients with severe endocrine system diseases (diabetes, thyroid disease), digestive system diseases (affecting VC absorption), cardiovascular system diseases, renal insufficiency (abnormal urine, imaging diagnosis, blood, pathological analysis confirms that kidney damage does exist, or glomerular filtration rate GFR <60mL/min), nervous system diseases such as dementia and epilepsy; patients with infectious diseases such as HIV, hepatitis, tuberculosis; patients with severe autoimmune diseases.
• Continuous alcohol or drug abuse (to avoid adverse reactions caused by drinking).
• Allergic to vitamin C or any component of the preparation.
• Patients who have already started large-dose (greater than 500mg/day) vitamin C supplementation.
• Unwilling to or stop taking supplements not provided by this project.
• Those who have participated in other ovarian aging clinical intervention projects.

We have decided not to share the IPD from this study due to concerns about participant privacy and confidentiality. Despite efforts to de-identify the data, there remains a risk of re-identification, which could compromise the privacy of the participants involved. Additionally, there are legal and ethical considerations that restrict the sharing of sensitive health information without explicit consent from the participants. Furthermore, the resources required to prepare and manage the data for external sharing are currently beyond our capacity. Therefore, to ensure the protection of our participants and comply with ethical standards, we have opted not to share the IPD at this time.

A double-blind design was employed for researchers were designed to be blinded. Allocation concealment was designed to apply to study subjects, clinical practitioners, outcome assessors and subsequent data analysts. The pharmaceutical company assigned numbers and labels to the drugs, and when study subjects were enrolled, they were assigned the corresponding drug number. The specific group corresponding to the number remained concealed from the project researchers, participants, and study subjects, with the blind data kept by independent personnel.

After the follow-up, independent personnel who maintained the blind data provided group information to the data analysts. The synthetic vitamin C, natural vitamin C and control groups were still represented as A, B and C, concealing the specific identities of the ABC groups from the data analysts. After the data comparison between the two groups the unblinding of the AB groups was conducted.