Last Updated on May 19, 2025 by Carrie Korem, FNTP
Is your body underconverting thyroid hormone? Are you producing enough T4, but not enough T3? The good news is that there are simple solutions for this! Let’s walk through my top 12 ways to improve thyroid hormone conversion (fT4 to fT3) naturally.
How does the thyroid make fT3?
Your thyroid produces fT4 and sends most of it to the liver to be converted into the active form, fT3. fT3 is the thyroid hormone that goes to every cell of the body.
If you’re under-converting, then you don’t necessarily have a thyroid problem, instead, you need to support your body so that it can make the conversion.
Where does the conversion of fT3 to fT4 happen?
The thyroid makes fT4 and sends most of it to the liver and then some to the gut, brain and peripheral tissues to be converted into fT3.
Since the liver takes on a large load of the conversion, supporting the liver is where I’ve found to be the best place to start when working with clients.
Due to the toxins we are exposed to on a daily basis from our food, air, water, body care, skincare, cleaning products, etc. it’s very common to struggle with liver congestion. If the liver cannot function properly, this can cause or contribute to low fT3. It can also cause estrogen dominance, severe headaches, blood sugar imbalance, chemical sensitivities, skin issues, and dark circles under the eyes, among other things.
As a Functional Nutritional Therapy Practitioner, I see this all the time, but the good news is there are some easy steps you can take to improve thyroid conversion.
The second most common reason for low fT3
If the body is under stress, then instead of fT4 being converted to fT3, it will be converted to reverse T3.
fT3 is the gas pedal of the body and rT3 is the breaks. So, if we have low fT3, we want to check our rT3 level so we can know if the low thyroid hormones are from stress.
Here are 12 ways to help improve thyroid conversion (fT4 to fT3):
1. Do a castor oil pack over your liver 3-4 times a week. As mentioned above, one of the major organs that takes care of fT4 to fT3 conversion is the liver, so it can be very helpful to support the liver with castor oil packs.
Here are instructions on how to do one, the supplies you’ll need and more about how they help the liver.
2. Eat a low-sugar, whole foods, nutrient dense diet.
One of the best things you can do for your body to increase your fT4 to fT3 conversion is to avoid processed foods and eat a nutrient-dense diet! Because the liver is responsible for filtering and neutralizing so many of the toxic substances we consume through our diet – alcohol, chemicals, excess hormones, and more – the cleaner we eat, the less load we put on our liver.
Keeping sugar intake around 20-30 grams or lower per day is important for optimal liver health. Too much sugar in the diet can actually lead to fatty liver disease and some studies show that sugar can be as damaging to the liver as alcohol.
The liver works with the pancreas and adrenals to keep blood sugar balanced in the body. If you struggle with blood sugar balance, it’s a good idea to take steps to correct this as it can have negative effects on the liver. See this article for more support on How to Balance Your Blood Sugar Naturally.
Please note that 20-30 grams of carbs does not include carbohydrates from healthy sources such as vegetables, soaked grains, raw dairy, etc.
3. Rub one drop of Zendocrine essential oil blend over your liver twice a day. I personally use it every day. It’s a blend of tangerine peel, rosemary leaf, geranium flower/leaf, juniper berry, and cilantro herb essential oils. It’s an amazing blend to add to your daily regimen to support the liver.
A little side note: I was on a real food diet for many years, and despite all of my efforts I would still get a break out on my chin each month before my cycle. These breakouts are usually hormone/liver related. So, I started using Zendocrine daily and it completely cleared up those annoying monthly breakouts! This has worked for so many others that I’ve shared this tip with!
4. Diffuse essential oils each day, such as lavender, lemon, balance, ylang ylang, etc. to reduce your stress and relax the body. Your sense of smell is directly connected to your emotional brain, so diffusing oils can immediately change how you feel and reduce stress. Stress puts strain on the adrenals, liver and pancreas and causes an imbalance in blood sugar levels (yes, this can happen even if you don’t eat sugar), so using oils each day to reduce cortisol levels will give your liver the support it needs to be able to work more efficiently.
5. Make sure you are eating enough carbohydrates. While a low-carb diet is all the rage right now, going too low carb can inhibit the conversion of fT4 to fT3 in the liver.
A minimum of 100g of carbohydrates a day from foods such as properly prepared legumes, lentils, potatoes and other starchy vegetables is a good place to start. And, if you’ve been on a very low-carb or grain-free diet for more than 12 months, I would consider talking to your practitioner about adding back some properly prepared gluten-free grains or fermented sourdough.
6. Eat two Brazil nuts a day. Brazil nuts contain selenium and this nutrient helps convert fT4 to fT3. I like to purchase raw Brazil nuts, soak them (to remove the phytic acid) and then dehydrate them in the oven. Check out my Instagram Story I did on this topic.
7. Take steps to reduce your cortisol and overall stress. Read my 17 Steps to Reduce Cortisol Naturally and see what steps you can add to your daily regimen. As mentioned above, when the adrenals are producing too much cortisol this can raise reverse T3 and lower free T3. It can also put a strain on the liver making it more difficult to convert free T4 to free T3.
8. Prioritize adequate quality sleep.
Research confirms that poor quantity and quality sleep is associated with Nonalcoholic Fatty Liver Disease (NFLD). and too little sleep, or poor sleep can increase cortisol levels during the day. Both of these things can decrease thyroid hormone conversion.
If you’re struggling with insomnia, here are my top tips.
9. Drink 1/4 a cup of beet kvass first thing in the morning, at least 10 minutes away from food. Beet Kvass is a tonic that helps decongest the liver.
10. Let go of anger and resentment and practice forgiveness. Negative emotions, most notably anger, can cause a significant burden to the liver which can reduce ft4 to fT3 conversion. In ancient medicine, certain emotions can correspond to particular organs. And imbalances in these emotions can lead to illnesses. A good book to read on this topic is, The Body Keeps the Score.
One research study identified specific patterns between emotions and corresponding bodily organ systems. It found that the liver was indeed closely tied to anger.
In this way, practicing forgiveness and releasing anger can do wonders for liver health. I suggest you talk to a counselor or therapist, someone you trust at your local church, or a friend that will help you walk through this process.
11. Consume foods rich in Vitamin A (aka retinol) daily. Vitamin A is actually essential for proper detoxification. It’s important to remember that Vitamin A is found only in animal foods. Your richest sources are liver (beef, lamb, duck, chicken), cod liver oil, butter, egg yolks, raw cream and cultured raw sour cream.
There is a HUGE misconception out there that vegetables, especially carrots and squashes, are excellent sources of vitamin A. This is absolutely false. Vegetables are wonderful sources of beta-carotene. But beta-carotene is only useful to humans as it is broken down and converted in the body to vitamin A by the body’s vitamin A stores.
This presents a tremendous challenge and serious health problem for vegans. This also explains why most long-term vegans eventually present with disorders linked to liver congestion and why it is not uncommon to see jaundice in vegans. While most vegans have good intentions, they may not have been properly educated as to the significant role vitamin A plays in detoxification as well as in skeletal formation and thyroid function.
12. Avoid intermittent fasting. While this is all the rage right now, most who are struggling with thyroid issues, need to avoid intermittent fasting because it puts too much strain on the adrenals and liver. Here’s more info on this topic.
Have you found other steps that have helped you increase your conversion of thyroid hormone? If so, please share in the comments below!
If you’d like to learn about some more important steps you can take to help support your thyroid, check out my class, “5 Keys to Thyroid Hormone Balance”. It’s just 45 minutes and I promise you’ll learn something new!
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