Dr. Axe Wire · Food, herbs & supplements · hormones

Vitamin C With Thyroid Medication Eased Hypothyroid Symptoms In Small Trial

A small placebo-controlled pilot gave 1 gram of vitamin C a day alongside levothyroxine and saw thyroid symptom scores fall further than with placebo.

By Dr. Axe Editorial Team · October 26, 2026 · 1 source · Watch

A double-blind pilot trial first published October 23, 2025 in Frontiers in Endocrinology, now circulating again, found that adding 1 gram of vitamin C a day to levothyroxine eased hypothyroid symptoms more than placebo in patients who needed high doses of the drug.

11patients finished

1g vitamin C daily

16weeks

Researchers in the United Arab Emirates first measured vitamin C in 26 hypothyroid patients and 91 healthy students: low levels showed up in 19.2% of patients versus 7.7% of controls, a gap that was not statistically significant. They then randomized 12 patients needing high levothyroxine doses to 1 gram of effervescent vitamin C or a pH-matched placebo, taken daily with the medication for 16 weeks; 11 finished. On the Zulewski score, a 12-item checklist of hypothyroid symptoms, the vitamin C group improved by 5.00 points versus 1.40 with placebo, a difference of 3.60 (95% CI 1.88 to 5.32). TSH fell 4.08 versus 2.35 mU/L, a difference whose confidence interval included zero. Neither group reported any side effects.

About half of people on levothyroxine may never reach a normal TSH and need dose changes, possibly because the tablet is poorly absorbed. Earlier work found vitamin C helped absorption in patients with gastritis; this trial did not measure absorption directly.

Thyroid Symptom Score Drop: Vitamin C vs Placebo

Frontiers in Endocrinology, 2025, Agha et al.

With six and five patients per group, chance differences mattered: average BMI was 26.6 kg/m² in the vitamin C group and 43.4 kg/m² on placebo. The symptom gap held after adjusting for starting values, and the authors call for a larger, stratified trial next.

Dr. Axe’s Take

This is the kind of simple, nutrient-based support I like to see tested. If your thyroid medication dose keeps climbing, ask why: poor absorption is a common underlying cause, and gut issues like celiac disease or H. pylori are worth checking. Vitamin C is inexpensive, and here symptoms improved more than on placebo. Regularly taking more than 1 gram a day can raise kidney stone risk, a known side effect, so talk with your doctor before adding it. If you're on levothyroxine, don't change it on your own; any change happens with your prescriber.

— Dr. Axe

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Story summary

Who: 11 adults with hypothyroidism needing high-dose levothyroxine (6 vitamin C, 5 placebo); phase 1 also tested 26 patients and 91 healthy students
Design: Double-blind, randomized, placebo-controlled pilot trial, first published 2025-10-23 in Frontiers in Endocrinology
Dose: 1 g effervescent vitamin C daily, taken with levothyroxine, for 16 weeks
Primary result: Symptom score down 5.00 points with vitamin C and 1.40 with placebo; gap 3.60 points (95% CI 1.88 to 5.32)
Secondary: TSH down 4.08 mU/L with vitamin C and 2.35 with placebo; gap 1.73 (95% CI from -2.14 to 5.60); starting BMI averaged 26.6 and 43.4 kg/m²
Funding / conflicts: Funder listed in the journal record: College of Medicine and Health Sciences, United Arab Emirates University. Conflict statement in the PubMed record: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.
Date: Oct 23, 2025