This study aims to evaluate the improvement of autoimmune status in patients with Type 1 Diabetes (T1D) through supplementation with 5-Methyltetrahydrofolate, and to explore the safety and efficacy of this treatment. The research seeks to provide new methods for the treatment of T1D and offer innovative ideas for enhancing the quality of life of T1D patients.

Inclusion Criteria:

1. Diagnosed with T1D based on the World Health Organization (WHO) classification criteria for disease diagnosis.
2. Aged 13-65 years, regardless of gender.
3. Duration of T1D ≤ 5 years.
4. Retained residual islet function, defined as fasting C-peptide > 0.1 nmol/L [0.30 ng/mL] or postprandial 2-hour C-peptide > 0.2 nmol/L [0.60 ng/mL].
5. Determined by the investigator to be capable and willing to: perform self-monitoring of blood glucose (SMBG); complete patient logs as required; receive diabetes education; and comply with the study treatment and visit schedule as per the protocol.

6) Signed informed consent form, with parental/guardian consent and signature required for pediatric/adolescent participants.

Exclusion Criteria:

1. Serum 5-methyltetrahydrofolate or folate levels exceeding the upper limit of the normal reference range.
2. Currently experiencing acute metabolic disorders, such as diabetic ketoacidosis or hyperosmolar hyperglycemic state.
3. Women who are breastfeeding, pregnant, or planning to become pregnant during the trial.
4. Received immunosuppressive or immunomodulatory therapy within the past year.
5. Comorbid with other autoimmune diseases, such as systemic lupus erythematosus.
6. Severe liver, kidney, gastrointestinal, hematologic, cerebral, or circulatory system diseases.
7. Psychiatric or neurological disorders leading to non-cooperation, non-adherence to medication, substance abuse, or other related issues.
8. Malignancy.
9. Recent surgery or significant stress.
10. Known hypersensitivity or allergic reaction to 5-methyltetrahydrofolate or its excipients.
11. Investigator's judgment of significant evidence of severe, active, or uncontrolled endocrine or autoimmune abnormalities.
12. Currently participating in another clinical trial.