Roadmap/07 - Supplementing T3/T4

Warning

• It is important to avoid creating deficiencies; when the metabolism is increased, demand for nutrients rises.
• If liver health is impaired, acute hunger may arise when skipping meals.
• It is wise to explore all other options and supplements before trying thyroid supplementation.
• Adequate cholesterol is required (above 160, ideally 200), as well as vitamin D and B intake so getting blood labs to check for things like total cholesterol, vitamin D, PTH, lactic acid, and prolactin will be useful references.
• Supplementing thyroid can sometimes reduce the rate of metabolism, by allowing cells to retain enough magnesium, which stabilizes ATP.
  • The goal is raising the efficiency, not burning as many calories as possible.
    • One community interpretation: burning through too many calories can be a sign of inefficient metabolism not producing sufficient ATP

Reasons to refrain from supplementing thyroid

• In rare cases, addressing the diet and factors such as sunlight, chronic stress/grief, etc. is enough to bring a person to euthyroidism.
• Thyroid supplementation requires constant self-awareness and willingness to experiment with dose and timing.

"Starting with 1 grain felt amazing at first, but caused adrenaline surges, overheating, and nightmares; splitting and eventually cutting to ¼–½ grain worked perfectly; then sunshine and better lifestyle made even that dose too much and I quit entirely." - HubblyBubbly Emporium

The average person (especially older, unwell, or depressed individuals) may not be capable of responsibly titrating or stopping thyroid medication on their own. One community account describes doctors often over-prescribing thyroid and being reluctant to adjust the dose once started (anecdotal, not a documented outcome).

Ray's articles

• Thyroid: Therapies, Confusion, and Fraud
• Thyroid, insomnia, and the insanities: Commonalities in disease  
• TSH, temperature, pulse rate, and other indicators in hypothyroidism
• Water: swelling, tension, pain, fatigue, aging

Symptoms associated with hypothyroidism

• Symptoms: Fatigue, lethargy, weight gain, cold extremities.
  • The full list of symptoms associated with hypothyroidism of common hypothyroidism symptoms here
• Physiological Biomarkers: Low body temperature, low pulse rate, slow reaction time, slow Achilles tendon reflex time.
• Blood tests: Generally, high TSH, cholesterol, PTH, and prolactin are associated with lowered thyroid function.

A more thorough self diagnosis can be found here.

Supplementation

It would be safe to start with T3 (triiodothyronine) only:

For more detail on T3 itself (structure, mechanism, and full dosing thresholds), see Triiodothyronine.

• Shorter half-life (~12 hours) makes gauging the effects easier.
• Small doses (1–3 mcg) can act within minutes.
• Helps stabilize glucose/glycogen, reduce adrenaline sensitivity, and gradually brings a sense of calm over several days.

T4 (thyroxine) is trickier:

For more detail on T4 itself (structure, mechanism, and the monotherapy critique), see Thyroxine.

• Longer half-life (~2 weeks) means it builds up slower within the tissues, and requires long-term planning.
• If liver function is impaired, T4 may convert to reverse T3, lowering metabolism.
• During the night and sleep, T4 can help suppress TSH and other stress hormones better than T3-alone.
• Oral T4 absorption needs adequate stomach acid; if TSH stays high despite a high T4 dose, consider H. pylori or other malabsorption before raising the dose further — direct T3 bypasses this absorption step entirely. See Thyroxine for the eradication-study numbers.

NDTs

Naturally Desiccated Thyroid supplements vary in their consistency and potency due to the varying diets and climates the animals were exposed to, which makes supplementing with them very tricky.

Purchase

Cynoplus (T4+T3) and Cynomel (T3) can be acquired from here and here.

Idealabs thyroid supplements can be purchased here, but keep in mind that a single drop contains too much thyroid, dosing may be inaccurate, and that T3 can be inactivated due to the solvents used.

Synthroid (T4 only) is usually what is prescribed by doctors, so finding a source of T3 and combining them would be the best way to approach.

Bad batches

• Thyroid medication is heat sensitive.
• Anecdotally, bad batches are a thing.
• If you’re not responding, it might be the batch.

DIY thyroid

You can theoretically, at least, make it yourself, if you for example boil milk with oysters or seaweed, a source of iodine and trace minerals, the prolonged boiling will create iodinated casein which in effect works like thyroid hormone, you can make it right in your kitchen, if it happened you are not able to buy thyroid in a pharma classical form. The reaction between trace minerals, casein, and iodine will produce an active thyroid-like substance.

— Ray Peat

Link to recipe

Dosing and possible deficiencies to watch out for

When you first start taking thyroid again, your tissues will need some extra magnesium, during the time when the dose is increasing, and when the mineral balance is restored your temperature and metabolic rate might decrease a little. Orange juice, milk, and coffee are good for the main minerals, while salting your food to taste.

— Ray Peat

Dosing should be approached carefully and methodically. The demand for nutrients goes up.

It is best to begin with the lowest dose and increase incrementally (every 2 weeks when supplementing with T4), while checking temperature and pulse. Around the end of the 2-week mark, the need for nutrients such as selenium (to convert the accumulated T4 to T3) magnesium, vitamin A, vitamin D3 and B vitamins (B1 and B3) may increase. Seafood such as tuna, shrimp, oysters and beef liver are all good sources of selenium, B vitamins, and Vitamin A.

People with a total cholesterol above 200, adequate vitamin A, and D, and minimal digestive issues respond best to thyroid.

Thyroid Calculator

Preparation	Amount	Unit	Note
Grains		grains	Pivot for all rows
NDT tablet mass		mg	~60 mg per grain (tablet weight)
NDT USP T3 content		mcg	~9 mcg T3 per grain (USP)
NDT USP T4 content		mcg	~38 mcg T4 per grain (USP)
T3-only rough equivalent		mcg	Rule of thumb: 25 mcg T3 ≈ 1 grain activity
T4-only rough equivalent		mcg	Rule of thumb: 100 mcg T4 ≈ 1 grain activity

Combined T3 + T4 (synthetic mix at chosen ratio)

Uses the same 25 mcg T3 ≈ 1 grain and 100 mcg T4 ≈ 1 grain activity model (not USP gland content). Peat often prefers T3-heavier mixes (e.g. 1∶2 or 1∶3 T3∶T4) than the default 1∶4.

Setting	Value
Desired Ratio (T3 : T4)	:
T3 mcg : T4 mcg (for selected grains)	:

T3 monotherapy

The metabolic effects of T3 last for 4 hours, but the TSH suppressing effects last a couple days. If you've been running on stress for a long time and relying on stress hormones for energy, taking T3 can have a "kick" to it as it sensitizes the adrenals, so starting with small amounts and splitting the dose throughout the day is smart. It may take several days for adrenaline levels to normalize. Salt and sugar are useful to keep the adrenaline "kick" at bay.

In Ray's experience, he consistently got heart palpitations from taking big dose of T3 as it made him severely hypothyroid by causing the liver to inactive the excess T3, so it's best to start with 1 mcg and adjust from there (anecdote as relayed by @RayPeatHeadShop, not a primary transcript).

Some contexts to consider

• Season
  • Lower doses in the warmer months; higher in colder months.
• Altitude
  • People at higher altitude naturally need less due to their increased retention of carbon dioxide.
• Protein intake
  • High protein diets can blunt thyroid activity due to the thyroid suppressing amino acids such as methionine, tryptophan, histidine, and cysteine.

Practical tips

• A pill crusher and milligram scale can be used for more accurate dosing since eyeballing can easily be inaccurate.
• It is paramount to check both pulse and temperature after dosing to measure any effects.
  • Salt, sugar, low-dose beta blockers, and cyproheptadine may be useful early on if adrenaline sensitivity is high.
  • Some supportive foods are gelatin, sugar, orange juice, chicken broth, milk, and ice cream. Even breathing into a paper bag for increasing tissue CO₂ can help.

Big picture

Thyroid supplementation is highly individualized. T3 offers quick, fine-tuned effects, while T4 requires patience and careful management. A complete diet and adequate micronutrition (selenium, magnesium, vitamins) is crucial for thyroid hormones to work effectively.

Demystifying Thyroid Supplementation summary sheet

Section	Takeaways	Notes
Symptoms	Low thyroid symptoms vary widely: fatigue, cold hands/feet, dry skin, low libido, etc.	No one-size-fits-all - use resting pulse (85 bpm) and morning temperature (~98°F) as the ideal markers to reach.
Dosing Strategy	Start low (e.g., 1/8 to 1/4 Cynoplus tablet); increase slowly every 2 weeks.	T4 builds up slowly (2-week half-life), so avoid changing the dose too soon.
T3/T4 Ratio	Peat favors T3-heavy ratios (1:3 or 1:2) vs standard 1:4 (T3:T4).	T3 supports brain, mood, energy and is more "brain protective".
Troubleshooting	Poor thyroid response may mean missing: protein, B-vitamins, magnesium, calcium, and carbohydrates.	Also check for vitamin D deficiency, infection, or excess dietary phosphate.
Cofactor Synergy	Thyroid increases metabolic rate → nutrient needs go up	Liver & oysters = best sources of critical cofactors (vit A, copper, selenium, zinc).
Climate Consideration	Colder weather may require a higher dose (e.g., 1 full tablet vs ¼ in a warm climate).	No one-size-fits-all - use resting pulse (85 bpm) and morning temperature (~98°F) as markers.

Barnes’ Standard Dose: ~2 grains/day (1 grain of NDT is USP-standardized to 9 mcg T3 + 38 mcg T4, not the 12.5/50 split sometimes quoted online).

Danny’s Personal Use: Cynoplus in evening (T4+T3), and Cynomel in daytime. Supplement according to need eg. more in the winter.

Ray’s Advice: Avoid taking >10 mcg T3 at once; eat with food to slow absorption. The liver naturally produces 3-4mcg of T3 every hour.

Stopping thyroid supplementation

Best to taper off slowly while measuring temperature, heart rate and food intake. Timing it so you don’t have any serious events coming up may be wise.

You might get sick or get headaches, brain fog, poor sleep and lose appetite for a couple days. It will stop after the thyroid resumes it's baseline function.

There are no long term negative effects of starting and stopping exogenous thyroid medication since the gland is quite versatile and will adjust its size and function within a day or two.

Anecdotally, some report that starting and stopping T3 resolved their hypothyroidism long-term when the underlying stress had been acute rather than lifelong; this is a community report, not a documented outcome.

Eating animal thyroid

People who eat fish heads or other animal heads generally consume the thyroid gland along with the brain. Historically this was a significant dietary thyroid source: fish heads, chicken necks, and traditional stews and sausages all included glandular tissue. This is a food-level, unmeasured source, not a substitute for dosed supplementation when a real deficiency is present.

Relevant quotes

By stabilizing your glucose and glycogen system, thyroid might be the basic thing that's needed. T3 acts quickly and is excreted with a half-life of about 12 hours. A dose of about 1 to 3 micrograms can have noticeable effects within a few minutes. If your adrenaline is very high (hypothyroid people can secrete it at 30 to 40 times the normal rate), the first doses can make you more sensitive to the adrenaline, so it's good to have the beta blocker, in case you react too strongly to the small dose. The T3 effects are already declining by the second hour, but it will have slightly increased your stored glycogen and reduced your adrenaline sensitivity, so reactions to each following dose should be better, and over a period of 2 or 3 days it should begin to have the calming, relaxing effects that are normal when the adrenaline is lower. Gelatin, sugar, and carbon dioxide have stabilizing, sedating effects, so things like chicken consomme, orange juice, ice cream, and re-breathing in a paper bag for a minute or two at a time might be helpful. Products containing thyroxine, T4, require planning on a longer range, considering that it accumulates in the body with a long half-life of about two weeks. Seafood provides the selenium needed for activation of the thyroid hormone.

— Ray Peat (2021)

I usually take 5 mcg with some milk and cheese, so that it absorbs gradually. If you crush the tablet, doses of 1 or 2 mcg every hour or two will produce very mild effects that you will be able to measure in your pulse rate and temperature. T3 is quick acting and has a half-life in the body of about one day, so it's important to check pulse rate 30 minutes to an hour after a dose of T3, during the first two or three days, until you find the right way to dose. Were you taking the T4 in a single dose per day? Doctors usually give that instruction. If your diet lacks something, such as selenium or vitamin D, that's needed for thyroid to work, T4 can interfere with the effects of T3; if you take 25 or 50 mcg in a single daily dose, the liver will experience a momentary toxic overdose, and over a period of a week or two will adapt its detoxification enzymes to destroy it, with the result that the body will be extremely deficient in thyroid most of the day, with a short period of toxic excess.

— Ray Peat (2018)

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