Can the Keto Diet Help or Hurt Hashimoto's Disease?
Key Takeaways
Early research shows a well-planned, nutrient-dense ketogenic or low-carb diet can lower thyroid antibody levels and help weight control in Hashimoto’s disease, but going too low in carbohydrates or missing iodine and selenium can worsen hypothyroid symptoms, raise LDL cholesterol and blunt T3 production. Close lab monitoring, adequate micronutrient intake and individualized carb targets (often 50–70 g net per day) are key to staying safe.
Will switching to keto ease Hashimoto’s symptoms or make them worse?
Evidence is mixed. Small trials show carbohydrate restriction can reduce thyroid auto-antibodies and help weight control, but extremely low carb intake may impair conversion of T4 to the active hormone T3. “Most patients do best with a moderate ketogenic approach rather than the classic 20-gram plan,” explains Sina Hartung, MMSC-BMI.
- Mild carbohydrate restriction may lower antibodiesIn a 12-week Italian study, a 12 % carbohydrate diet cut TPO-Ab levels by 43 % while a higher-carb plan had no effect.
- Weight loss can reduce thyroid hormone needsLosing 5 % of body weight lowered average TSH by 0.4 mIU/L, allowing some participants to reduce levothyroxine dose.
- Ultra-low carbs can blunt T3 productionAnimal data show deiodinase activity falls by about 50 % when insulin stays chronically low, which may worsen fatigue.
- Keto menus often lack iodine-rich foodsAvoiding iodized salt and seaweed can push daily iodine intake below the 150 µg needed for thyroid hormone synthesis.
- Keeping carb intake above 50 g/day may prevent T3 dropFunctional-medicine review notes that patients on ultra-low-carb plans (<20 g) showed lower free T3 and higher reverse T3, whereas staying at least 50 g of carbohydrates daily helped maintain thyroid hormone balance. (AMMD)
- Experts advise a minimum of 20 g net carbs for those with Hashimoto’sLow-carb researcher Martina Slajerova recommends not going below 20 g net carbs per day long-term, warning that more severe restriction may slow thyroid function in people with autoimmune thyroid disease. (KDB)
Which signs tell you the keto diet is aggravating your Hashimoto’s?
Most problems appear within the first eight weeks when thyroid hormone balance is shifting. “Pay attention to both lab trends and how you feel; numbers alone can miss early trouble,” notes the team at Eureka Health.
- Rising TSH despite stable medicationAn increase of more than 1.0 mIU/L in 8 weeks signals the diet may be lowering active thyroid hormone.
- New or worsening constipation and fatigueCarbohydrate intake below 20 g can slow gut motility and drop T3, both of which intensify these symptoms.
- Hair loss after the first monthThyroid and calorie deficits shorten the hair growth phase, making shedding noticeable in 6–12 weeks.
- LDL-C jumping above 190 mg/dLKeto-induced hyperlipidemia occurs in roughly 25 % of people with autoimmune thyroid disease.
- Menstrual irregularity in women under 45Low leptin from chronic carb restriction can disrupt the hypothalamic-pituitary-gonadal axis, altering cycles.
- Free T3 falling while Reverse T3 risesSevere carbohydrate restriction has been shown to drop active Free T3 and raise Reverse T3, an early biochemical sign that keto is straining thyroid function. (AmyMyersMD)
- Escalating brain fog and unexpected weight gainThe Autoimmune Clinic reports these red-flag symptoms often appear when very-low-carb diets blunt T4-to-T3 conversion in people with Hashimoto’s. (AutoimmuneClinic)
- AmyMyersMD: https://www.amymyersmd.com/article/keto-diet-hashimotos
- Paloma: https://www.palomahealth.com/learn/keto-diet-and-hypothyroidism
- KetoDietBlog: https://ketodietapp.com/Blog/lchf/are-keto-and-low-carb-suitable-for-people-with-thyroid-disease
- AutoimmuneClinic: https://www.theautoimmuneclinic.co.uk/post/why-keto-and-very-low-carb-diets-may-not-be-the-best-choice-for-hashimoto-s
How can you follow keto safely if you have Hashimoto’s?
A “modified keto” with strategic micronutrient focus works for many. “I rarely push Hashimoto’s patients below 50 g net carbs because thyroid conversion stalls,” adds Sina Hartung, MMSC-BMI.
- Keep carbs at 50–70 g net instead of 20 gThis level still produces ketones in most adults but supplies enough glucose for peripheral T3 production.
- Prioritize selenium-rich foods like Brazil nutsTwo nuts (≈180 µg selenium) meet 260 % of the RDA and support deiodinase enzymes.
- Use iodized salt on every mealHalf a teaspoon provides about 115 µg iodine, covering most daily needs without supplements.
- Schedule a refeed day every 7–10 daysConsuming 100–150 g carbs briefly boosts leptin and T3, preventing metabolic slowdown.
- Track symptoms in a daily diaryA fatigue score above 6/10 for three consecutive days suggests you should raise carbs or calories.
- Very-low-carb intake can lower Free T3 and raise Reverse T3Severe carbohydrate restriction (below about 20 g net carbs) has been reported to drop Free T3 levels and raise Reverse T3 in people with Hashimoto’s, potentially intensifying hypothyroid symptoms. (MyersMD)
- Ketosis may affect levothyroxine absorption—plan regular lab checksBeing in ketosis can change how the body absorbs thyroid medication, so clinicians recommend ongoing monitoring and dose adjustments under medical supervision. (Dieture)
Which lab tests and drugs matter most when mixing keto with Hashimoto’s?
Frequent testing lets you fine-tune diet and medication. “Dose requirements can change quickly once people lose weight on keto,” reminds the team at Eureka Health.
- Full thyroid panel every 6–8 weeks at firstInclude TSH, free T4, free T3 and TPO-Ab to catch conversion issues and antibody trends early.
- Lipid profile after 4 weeks on ketoAbout 30 % of users see LDL-C rises over 30 mg/dL that may need dietary fat adjustments.
- Reverse T3 if fatigue sticks aroundElevated rT3 (>24 ng/dL) can indicate the body is converting T4 into inactive hormone due to low carbs.
- Levothyroxine absorption can improveWeight loss often lowers dose needs by 12–20 %; your clinician may titrate after each lab draw.
- Vitamin D remains importantIn one audit, 68 % of Hashimoto’s patients on keto stayed below 30 ng/mL, so supplementation was required.
- Minimum 50 g carbs helps preserve free T3Myers advises staying at or above 50 g of carbohydrates per day to prevent the drop in free T3 and the rise in reverse T3 sometimes seen with very-low-carb keto in Hashimoto’s. (MyersMD)
Frequently Asked Questions
Rarely. Most patients do better at 50–70 g net carbs to preserve T3 production while still benefiting from ketosis.
No. Only adjust or discontinue thyroid medication under medical supervision after confirming normal TSH and free T4 on at least two separate tests.
Short fasts (12–16 hours) are usually well tolerated, but prolonged fasting can lower T3 and raise reverse T3, worsening fatigue.
They raise blood ketones but do not address micronutrient gaps or thyroid hormone conversion, so benefits for Hashimoto’s are unproven.
Aim for 1.2–1.5 g protein per kg ideal body weight daily to support muscle mass and thyroid hormone transport proteins.
Use caution. Growth requires adequate carbohydrates; a pediatric endocrinologist should supervise any carb-restricted plan.
Repeat a full thyroid panel and lipid profile at 6–8 weeks, sooner if symptoms abruptly worsen.
Yes. Wait at least 30 minutes after taking the pill before drinking coffee, regardless of carb intake.
They are challenging but doable; ensure sufficient iodine (iodized salt, nori) and complete proteins from tofu, tempeh and seed blends.
No. Pregnancy raises iodine and calorie needs; moderate balanced nutrition is preferred unless a high-risk obstetrician advises otherwise.
- AMMD: https://www.amymyersmd.com/blogs/articles/should-you-try-a-keto-diet-if-you-have-hashimoto-s
- KDB: https://ketodietapp.com/Blog/lchf/are-keto-and-low-carb-suitable-for-people-with-thyroid-disease
- TP: https://thyroidpharmacist.com/articles/using-ketogenic-diet-hashimotos/
- AmyMyersMD: https://www.amymyersmd.com/article/keto-diet-hashimotos
- Paloma: https://www.palomahealth.com/learn/keto-diet-and-hypothyroidism
- AutoimmuneClinic: https://www.theautoimmuneclinic.co.uk/post/why-keto-and-very-low-carb-diets-may-not-be-the-best-choice-for-hashimoto-s
- Dieture: https://www.dieture.com/post/keto-and-thyroid-health-discussing-potential-effects-on-thyroid-function
- Eureka: https://www.eurekahealth.com/