You’re exhausted. Your hair is thinning, your skin feels like parchment, and you’re gaining weight despite eating like a rabbit. You go to the doctor, they run a TSH test, and tell you everything is "fine." But it isn't fine. Often, the missing piece of that puzzle is a sneaky little metabolite called Reverse T3 (rT3). If you want to know how to fix high reverse t3 naturally, you have to stop looking at the thyroid as an isolated gland and start looking at it as a survival mechanism.
Reverse T3 is basically the "brake pedal" for your metabolism. While Free T3 is the gas that gives you energy, rT3 steps in to slow everything down. This isn't a "glitch" in your body. It’s actually a very sophisticated defense strategy. Your body thinks it's starving, or under attack, or too sick to function, so it creates rT3 to conserve energy. The problem is that in our modern, high-stress world, that brake pedal gets stuck to the floor.
The Science of Why rT3 Hijacks Your Energy
To understand how to fix high reverse t3 naturally, we have to look at the conversion process. Your thyroid mostly produces T4, which is an inactive storage hormone. Your liver and kidneys (and other tissues) then convert that T4 into either the active T3 or the inactive rT3. Think of T4 like a raw material that can be turned into either a tool or a paperweight. When you’re healthy, you make tools. When you’re stressed, you make paperweights.
Enzymes called deiodinases handle this. Specifically, the D1 and D2 enzymes create active T3, while the D3 enzyme creates rT3. When cortisol is high—or when there is systemic inflammation—the D3 enzyme becomes the dominant player. It’s a literal biological pivot. This is why you can have "normal" T4 levels on a lab test but still feel like you're moving through molasses. The "pool" of hormone is there, but it’s being diverted into the wrong channel.
Stop the Stress Response Cold
You can’t talk about thyroid health without talking about the adrenals. It’s a cliché because it’s true. High cortisol is the primary driver of rT3 production. When the brain perceives a threat—whether that’s a looming work deadline or a literal bear—it signals the thyroid to slow down via the HPT axis.
Honestly, most people try to "supplement" their way out of this while still drinking four cups of coffee and sleeping five hours a night. It won't work. You have to lower the physiological load. This means prioritizing sleep like it’s your full-time job. Dr. Izabella Wentz, a well-known pharmacist and thyroid expert, often points out that "adrenal safety" is the first step in thyroid recovery. If your body doesn't feel safe, it will keep making rT3 to protect you from burning out your "engine."
Try focusing on restorative movement rather than high-intensity interval training (HIIT). While HIIT is great for some, if your rT3 is climbing, that 6:00 AM CrossFit class is just adding more fuel to the inflammatory fire. Switch to walking or restorative yoga for three weeks and watch what happens to your labs.
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The Nutrient Deficiencies Hiding in Plain Sight
Your body needs specific "spark plugs" to run the conversion enzymes correctly. If you're missing these, the D1 and D2 enzymes simply can't do their jobs.
Selenium is non-negotiable. The conversion of T4 to T3 requires selenium-dependent enzymes. A study published in The Lancet highlighted how selenium deficiency directly impairs thyroid hormone metabolism. You don't need a massive dose; just two or three Brazil nuts a day can often provide the 200mcg typically recommended by functional medicine practitioners.
Iron and Ferritin. This is a big one that doctors often miss. If your ferritin (stored iron) is below 60–70 ng/mL, your thyroid conversion will likely suffer. Iron is a cofactor for the heme-dependent thyroid peroxidase enzyme. Without it, you're stuck in the rT3 loop. But don't just pop iron pills—test your levels first, because iron overload is just as damaging as deficiency.
Zinc and Copper balance. These two minerals work in a delicate dance. Zinc is required for the TRH receptor in the brain to signal the thyroid properly. If you’ve been taking high doses of zinc to avoid getting sick, you might have depleted your copper, which ironically can also stall thyroid function.
Gut Health and the "20 Percent" Rule
Did you know that about 20% of your T4 to T3 conversion happens in the gut? It’s true. An enzyme called thyroid sulfatase, produced by healthy gut bacteria, converts inactive T3 sulfate and T3AC into active T3. If you have dysbiosis—an imbalance of bad vs. good bacteria—that 20% conversion simply doesn't happen.
This is why people with SIBO (Small Intestinal Bacterial Overgrowth) or "leaky gut" often have high rT3. The inflammation caused by gut permeability triggers the release of cytokines like TNF-alpha and IL-6. These cytokines are like a "stop" sign for T3 production. If you want to fix high reverse t3 naturally, you have to address the bloating and the digestive distress. It's all connected.
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The Calorie Trap
Dieting is one of the fastest ways to spike your rT3. When you go on a "crash diet" or drastically cut your carbohydrates, your body interprets this as a famine. In response, it ramps up rT3 to lower your basal metabolic rate. It’s trying to keep you alive.
Low-carb diets like Keto are popular for weight loss, but for some women especially, they can be a disaster for the thyroid. Insulin is actually needed for the conversion of T4 to T3. If insulin levels are chronically too low, T3 levels drop and rT3 rises. If you're struggling with high rT3, try adding in "clean" carbs like sweet potatoes, berries, or squash. Sometimes, simply eating more is the secret to fixing a "broken" metabolism.
Liver Congestion: The Traffic Jam
The liver is the primary site of T4 to T3 conversion. If your liver is bogged down by environmental toxins, alcohol, or even a high-fructose diet, thyroid conversion takes a backseat to detoxification. Think of your liver like a filter. If the filter is clogged, nothing flows through it efficiently.
Supporting the liver doesn't mean doing a "juice cleanse." It means giving the liver the amino acids it needs for Phase II detoxification. Glycine, taurine, and cysteine are vital. Eating enough high-quality protein is actually a liver-supportive strategy. Milk thistle and dandelion root tea can be helpful, but they aren't substitutes for a solid nutritional foundation.
Inflammation: The Invisible Driver
Systemic inflammation is the silent killer of T3. Whether it's from a chronic low-grade infection (like Epstein-Barr virus), food sensitivities (like gluten or dairy), or environmental toxins (like mold), inflammation tells the D3 enzyme to start churning out rT3.
If you’ve checked the boxes on stress and nutrients but your rT3 is still high, look for hidden inflammation. Gluten is a common culprit because the molecular structure of gliadin (a protein in wheat) closely resembles thyroid tissue. This is called molecular mimicry. Your immune system attacks the gluten, gets confused, and starts attacking the thyroid, leading to inflammation that drives up rT3.
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Identifying the "Normal" Lab Range Trap
When you get your results, the "standard" lab range for rT3 is usually quite wide—often something like 9 to 24 ng/dL. But functional medicine experts like Dr. Amy Myers argue that "normal" isn't the same as "optimal."
Most healthy people have an rT3 level on the lower end of that scale, typically below 15 ng/dL. More importantly, you should look at the T3/rT3 ratio. You want your Free T3 to be significantly higher than your Reverse T3. If you divide your Free T3 by your Reverse T3 (using the same units), the ratio should ideally be 20 or higher. If it's lower, you're in a state of thyroid resistance.
Practical Steps to Lower Your Numbers
Fixing this isn't about one "magic pill." It's a multi-pronged approach to convince your body that the "famine" is over.
- Test, don't guess. Get a full thyroid panel: TSH, Free T4, Free T3, Reverse T3, and Thyroid Antibodies (TPO and TgAb). Also, check your Ferritin and Vitamin D.
- Audit your stress. This sounds fluffy, but it’s physiological. If you’re in "fight or flight" mode all day, your rT3 will stay high. Use box breathing or meditation to signal to your nervous system that you are safe.
- Eat enough. Especially carbohydrates if you’ve been low-carb for a long time. Aim for at least 100-150 grams of whole-food carbs per day to support conversion.
- Supplement strategically. Consider a high-quality Selenium (200mcg) and Zinc (15-30mg) supplement. If your ferritin is low, work with a practitioner to gently raise it.
- Clean up your environment. Reduce your exposure to endocrine disruptors found in plastics (BPA/BPS), "fragrance" in perfumes, and harsh cleaning chemicals. These occupy receptor sites that T3 should be using.
- Address the gut. If you have gas, bloating, or irregular movements, work on healing the gut lining. Bone broth, fermented foods (if tolerated), and a high-quality probiotic are good starting points.
Moving Forward With a Plan
Correcting a thyroid imbalance takes time. You didn't get high rT3 overnight, and you won't fix it in a week. Usually, it takes about three to six months of consistent lifestyle and nutritional changes to see a significant shift in your lab work and, more importantly, how you feel.
Focus on the low-hanging fruit first. Are you sleeping? Are you eating enough? Are you taking your selenium? Once those foundations are set, the more complex pieces—like gut health and heavy metal toxicity—become much easier to tackle. Listen to your body; that "tired but wired" feeling is a direct signal that your rT3 is likely winning the battle. It’s time to help your body tip the scales back toward active energy.