Condition

Hashimoto's disease

Hashimoto's disease is an autoimmune condition in which the immune system gradually attacks the thyroid gland, cutting the hormones it makes and often causing an underactive thyroid. Among supplements, selenium has the strongest evidence, but studies of Hashimoto's signs found no clear difference, and one small carnitine study found bone density improved. Vitamin D has moderate evidence, yet most findings come from small studies, so conclusions remain tentative.

Sources: PMID 15591013

Supplements studied: 3
Graded outcomes: 3
Trials: 3
People studied: 1,977

Evidence by supplement

Strong
Moderate
Limited
Very limited

3 supplements

L-Carnitine

L-Carnitine: outcomes studied for Hashimoto's disease
Grade	Outcome	Effect	Size	Studies	People
	Bone Mineral Density Small Improvement	Improves (the measure goes up)	Small effect	1 study	50 people
Studies that measured bone mineral density Effects of carnitine on thyroid hormone actionAnn N Y Acad Sci · PMID 15591013
	Total cholesterol	Improves (the measure goes down)		6 studies	50 people
Studies that measured total cholesterol Effect of oral L-carnitine administration on insulin sensitivity and lipid profile in type 2 diabetes mellitus patientsAnn Nutr Metab · PMID 18714152 Effects of carnitine on glucose and lipid metabolic profiles and fertility outcomes in women with polycystic ovary syndrome: A systematic review and meta-analysis.Clin Endocrinol · PMID 36746677 Oral carnitine supplementation reduces body weight and insulin resistance in women with polycystic ovary syndrome: a randomized, double-blind, placebo-controlled trialClin Endocrinol · PMID 26666519 and 3 more on the L-Carnitine page
	Liver Enzymes	Changes; see studies		2 studies	50 people
Studies that measured liver enzymes Data from a randomized and controlled trial of LCarnitine prescription for the treatment for Non- Alcoholic Fatty Liver DiseaseBioinformation · PMID 25352725 Effects of carnitine supplementation on liver aminotransferase enzymes: A systematic review and meta-analysis of randomized controlled clinical trialsIndian J Gastroenterol · PMID 31828538
	Hyperthyroidism Symptoms	Improves (the measure goes down)		1 study	50 people
Studies that measured hyperthyroidism symptoms Usefulness of L-carnitine, a naturally occurring peripheral antagonist of thyroid hormone action, in iatrogenic hyperthyroidism: a randomized, double-blind, placebo-controlled clinical trialJ Clin Endocrinol Metab · PMID 11502782
	Weight	Improves (the measure goes down)		1 study	50 people
Studies that measured weight l-Carnitine Supplementation in Older Women. A Pilot Study on Aging Skeletal Muscle Mass and FunctionNutrients · PMID 29473908
	Ferritin	Improves (the measure goes up)			50 people
	Osteocalcin	Improves (the measure goes up)			50 people
	Sex Hormone Binding Globulin	Improves (the measure goes up)			50 people

Iodine

Iodine: outcomes studied for Hashimoto's disease
Grade	Outcome	Effect	Size	Studies	People
	Serum T4 Small Decrease	Improves (the measure goes down)	Small effect		300 people
	Thyrotropin Releasing Hormone	Improves (the measure goes up)		1 study	300 people
Studies that measured thyrotropin releasing hormone Effect of low dose iodide supplementation on thyroid function in potentially susceptible subjects: are dietary iodide levels in Britain acceptableClin Endocrinol · PMID 2060151

Selenium

Selenium: outcomes studied for Hashimoto's disease
Grade	Outcome	Effect	Size	Studies	People
	Hashimoto's Thyroiditis Signs No effect		NoneNo effect		1,377 people
	Thyroid-Stimulating Hormone	Improves (the measure goes up)		1 study	939 people
Studies that measured thyroid-stimulating hormone Clinical efficacy of selenium supplementation in patients with Hashimoto thyroiditis: A systematic review and meta-analysis.Medicine · PMID 40898469
	Serum T3	Improves (the measure goes up)			432 people
	Serum T4	Improves (the measure goes up)			776 people
	Subjective Well-Being	Improves (the measure goes up)			171 people

Key findings

Bone Mineral DensityL-CarnitineImproves (the measure goes up)
Serum T4IodineImproves (the measure goes down)
Hashimoto's Thyroiditis SignsSelenium

The Hashimoto's Thyroiditis Supportive Care protocol

2 primary supplements · 6 supporting supplements

Selenium200 mcg daily (selenomethionine form preferred)
Vitamin D2,000–5,000 IU daily (target 40–60 ng/mL)

See the full protocol

Studies cited

1 study from PubMed

Efficacy of the Autoimmune Protocol Diet as Part of a Multi-disciplinary, Supported Lifestyle Intervention for Hashimoto's ThyroiditisCureus · PMID 31275780