Before You Take Lugol's Iodine...

If you're thinking about taking Lugol’s iodine, I have a warning for you. There’s some information that most people are unaware of - iodine can be dangerous!

Now, before you get your knickers in a knot, yelling at me and unsubscribing, hear me out. I’m not saying don’t take it. What I’m saying is there’s something you need to check before you do. This is something most of the people online who are telling you how much you need iodine aren’t talking about, and something that I wish someone HAD told me before I ended up hyperthyroid.

So let’s start with my story...

I became hyperthyroid when I was about 45 years old, and it was because I’d been taking Lugol’s iodine.

The reason it happened had nothing to do with taking too much. But rather, it had everything to do with a mineral that most people have never even thought about in relation to their thyroid.

And that mineral is selenium.

I suspected I was hypothyroid from quite a young age. I had many common symptoms of hypothyroidism, but my (TSH) tests came back normal, and the doctors said there was nothing wrong.

So I started to look for answers from other sources.

I’d been hearing about iodine for a while — the idea that we’re all depleted, that the thyroid needs it, and that it can transform your energy and your health.

I read a popular book on the topic called ‘Iodine: Why You Need It and Why You Can’t Live Without It’ by Dr David Brownstein. It was a good book! (You can find the link on my favourite books resources page here). Dr Brownstein has made thyroid and iodine his specialty. He is a well-known voice on thyroid health and an advocate for iodine supplementation.

But the early version of his book that I read all those years ago didn’t focus on nutritional cofactors or selenium at all. The whole focus back then was on iodine and salt. Other nutrients didn’t seem to be part of the protocol. Apparently, this has changed in the newer versions of his book, which is good to hear.

I decided to try the protocol from the book. I got some Lugol’s iodine solution, and I started taking it. Initially, I had great results. I’d had fibrocystic breasts for years, and that changed dramatically, so the iodine was obviously something my body needed.

But then over time, things started to shift.

When I look back, I now realise that while taking the Lugol’s, slowly, over time, I’d become MORE hypothyroid. But I didn’t recognise it at the time. The symptoms had been part of my life off and on forever. I had other stuff going on in my life, and I probably just put it down to stress.

My feet were swelling, I was gaining weight, my brain wasn’t working well, and I was struggling to exercise because my energy was lacking.

But then, about a year or eighteen months after I started on the Lugols, things shifted in a new direction and got a bit crazy.

I was an emotional mess. I cried a lot. My poor husband didn’t know what was going on.

• I was hot and itchy.

• My hair was falling out.

• My heart rate went up, and I had a resting heart rate of 160 beats per minute!

• I felt wired, anxious, like I was running on adrenaline all the time.

• I was struggling to type even though I’d been typing since I was 14 years old.

• I was having panic attacks.

• I was irritable.

• And I quickly lost all my muscle mass.

I went from lifting heavy weights at the gym six days a week and running on the beach, to needing help to get up two steps at the beach, and I was unable to get myself up off the floor.

In the end, the symptoms were not subtle! My body was clearly struggling.

I had no idea what was happening to me. I made an appointment with a functional medicine doctor, assuming my symptoms were something to do with my thyroid, menopause and maybe stress.

Luckily, she did the right tests and found I was very hyperthyroid.

That’s not what I expected because I hadn’t lost weight at the time I was diagnosed.

But my symptoms were getting crazier by the day...

I stopped taking the iodine. I didn’t see the endocrinologist the doctor wanted me to see, but instead decided to sort the problem out myself, which I did over the coming months.

And I did some digging into what had actually happened.

At the time, I realised it was possibly due to not having the right nutrients to go with the iodine, but I wasn’t clear on what I’d done wrong. I’d been following the protocol in the book, and so I wondered if it was just my body. My body always seems to be ultra sensitive, and it does weird shit that I don’t expect.

But now I know differently. What I’ve discovered in more recent times has surprised me — not because the science is obscure, but because it’s almost never talked about in the iodine conversation.

What I had experienced has an actual name. It’s called the Jod-Basedow effect. (pronounced yot-bah ze doh - German) And it happens when you load iodine into a thyroid gland that isn’t prepared to handle it.

The Jod-Basedow effect — Jod is simply the German word for iodine - and it is a phenomenon where giving iodine to someone deficient in it, or to someone with certain thyroid conditions, triggers a burst of excess thyroid hormone production.

So think of it this way. Your thyroid gland is basically a hormone factory. Its job is to take iodine and use it to build thyroid hormones — primarily T4, and then T3, which is the active form your body actually uses.

If your thyroid has been running low on iodine for a while, and then suddenly you flood it with a concentrated dose, it can go into overdrive. It’s like a factory that’s been running on limited supplies suddenly getting a massive shipment — and ramping up production far beyond what the body needs.

The result is temporary hyperthyroidism.

Your thyroid hormones spike. And that feels awful. Heart palpitations, anxiety, insomnia, feeling overheated, rapid pulse — these are all classic hyperthyroid symptoms.

This is one way people can become hyperthyroid from taking iodine.

But there’s another reason this happens.

The part that most people miss entirely is that your thyroid doesn’t just need iodine to make hormones. It needs selenium to regulate the process.

Selenium is a trace mineral, and in the context of thyroid function, it does several critical jobs. The first one is that selenium is required to make a family of enzymes called selenoproteins. They’re called that because they’re literally made from selenium.

And one group of those, the deiodinases, are literally responsible for converting T4 into T3. So, without adequate selenium, your thyroid hormone conversion is already compromised before you even add iodine into the equation.

But the second job is the one that’s directly relevant to what happened to me.

When your thyroid produces hormones, it generates hydrogen peroxide as a byproduct of that process. Hydrogen peroxide is essentially an oxidative byproduct. It’s reactive, and left unchecked, it damages the thyroid tissue itself.

Under normal circumstances, a selenium-dependent enzyme called glutathione peroxidase neutralises that hydrogen peroxide. It acts like a quenching system, mopping up the oxidative stress and protecting the thyroid gland.

Now imagine what happens when you flood that system with iodine. You’re dramatically ramping up hormone production, but you don’t have enough selenium on board to activate the glutathione peroxidase that’s supposed to contain it and protect the gland.

You get a surge of hormone production, inadequate antioxidant protection, and thyroid tissue hit with oxidative damage. This scenario is actually a double hit: a hyperthyroid response AND ongoing gland damage.

This is exactly why the research shows that selenium deficiency is a major risk factor for the Jod-Basedow effect, and for iodine-induced thyroid problems more broadly.

So this is what happened to me, as I said. I started taking iodine and had good results in other areas of my body. But what I didn’t know was that it was causing problems over time and damaging my thyroid gland because I was lacking in selenium.

And to make things worse, I’ve recently learned that I have another factor that came into play here.

I’ve learned that I have DIO1 genetic variants. Not just one, but several. These are the SNPs that are responsible for making the enzyme that converts T4 to T3, and selenium is even more important for people with these variants because thyroid hormones are possibly going to be deficient even with optimal selenium. I won’t go into too much detail about that here. It’s another article for another day. But suffice it to say that approximately 25% of the population has these variants in some form. It’s not rare.

»Read my article about DIO1 and DIO2 variants here.

So, who does this affect? Is it everyone, or is it a subset of people?

The honest answer is: it’s a larger subset than you might think, and there are several overlapping groups where the risk is meaningfully elevated.

This is the one most people don’t realise. Selenium in your diet comes from the soil. If the soil in your region is depleted, the food grown in it is also depleted — and you won’t make that up just by eating well. New Zealand (where I currently live) is particularly affected.

Parts of Australia are also well-known examples of this, although some parts of Australia have good levels, which helps to keep the selenium intake of the Australian population a little higher, overall.

Selenium levels in New Zealand soils are among the lowest in the developed world, which means people eating a predominantly local land-based diet are very likely to be running low in selenium, often without knowing it. This isn’t a niche concern for us; it’s a real baseline issue that’s being ignored by the medical system and the New Zealand government.

I personally believe every doctor in New Zealand should be testing patients regularly for selenium deficiency, and I think the government should be letting Kiwis know that this is a potential problem. I’ll be writing more about this specifically in the future, so keep an eye out for more content on this topic.

The next group of people at risk are those who’ve been iodine-deficient for a long time. If your thyroid has been adapted to running on low iodine, it becomes, in a sense, sensitised. The gland may have developed nodules or areas of autonomous function, meaning parts of it can act independently of the normal regulatory signals.

When you add iodine, those areas can go rogue and produce hormones without the usual checks. This is particularly relevant for older adults and anyone who’s been on a restricted or unconventional diet for years.

Nodular thyroid disease is more common than most people realise. It often causes no symptoms and goes undetected for years. If you have nodules, particularly autonomous ones, iodine loading is a real risk.

Then there are people with underlying autoimmune thyroid conditions. Particularly Hashimoto’s. I had wondered originally if this was my problem. The oxidative cascade I described earlier is especially dangerous in an already-inflamed thyroid. Iodine can act as an accelerant.

And then there are those of us with certain genetic variants. The enzymes that manage thyroid hormone production and protection are genetically encoded. Variants in the DIO1 and DIO2 genes affect how efficiently you convert T4 to T3.

Variants affecting the MTHFR pathway affect your overall methylation and antioxidant capacity.

And some people simply have a genetically lower baseline capacity for selenium utilisation, meaning even if they’re eating a selenium-adequate diet, their body isn’t using it as efficiently as it should. These are the people for whom selenium status is even more critical before touching iodine.

As much as influencers online like to make out that we’re all the same, we’re not. This is the danger of telling viewers to take iodine without understanding the potential risks. They’re very real.

Where does this leave you? Is iodine off the table entirely? Not necessarily. But the sequence matters enormously.

The first thing I’d suggest, based on what I’ve learned, is to get your selenium status sorted before you even consider iodine supplementation. I’m personally aiming for the optimal range of 1.6-1.9 umol/L - not just ‘in range’. If you’re in New Zealand or Australia, or any other areas of the world with low selenium, assume you are probably low unless you’ve tested or you’re actively supplementing from a reliable source.

And if you’re supplementing, I think you still need to test because if you take too much for too long, that’s also dangerous. Selenium can be toxic if we have too much in the body. Personally, I’ll be testing once or twice a year from now on, just to see where my levels are at.

When it comes to nutrients, food sources are always the best, and the best food sources of selenium are organ meats, liver in particular, and seafood. Brazil nuts are often cited, but they’re wildly variable in selenium content. It’s easy to overshoot with them, which has its own problems, as I’ve mentioned.

If you’re eating nose-to-tail or doing a carnivore or ketovore-style diet, you’re doing better than most people, but depending on where your food comes from, it may still not be enough.

For supplementation, selenomethionine (the natural version of selenium) and selenium from whole food or natural algae sources are generally well absorbed.

I’d consider whether you actually need concentrated iodine. Most people doing a seafood-inclusive diet, or who regularly eat seaweeds like dulse or kelp, are getting meaningful iodine without the risk of a sudden large dose. Whole food iodine is much gentler on the system than Lugol’s, and it comes pre-packaged with all the cofactors that help your body handle it.

If you do want to use Lugol’s, and you’re satisfied your selenium status is adequate, start at the absolute lowest dose and increase slowly. Do not follow protocols that advocate starting high or jumping to high therapeutic doses. That’s a recipe for exactly the kind of response I described.

And if you’ve had any hyperthyroid episode in the past — palpitations, anxiety, heat intolerance, unexplained weight loss — please talk to someone who can run proper thyroid panels before you go near iodine supplementation.

The bottom line is this. Iodine and selenium are not optional partners. They are required partners. The research on this is clear and when you look at populations with iodine deficiency AND selenium deficiency, the outcome is almost always worse than deficiency in either one alone.

The cruel irony of the iodine conversation online is that the people who are most enthusiastic about supplementing iodine are often exactly the people eating unconventional diets — carnivore, ketovore, low-processed-food — who are also most likely to have thought about nutrient density. But selenium is one nutrient that tends to get missed.

So before you reach for that dropper bottle: check your selenium. It’s a simple blood test. Make sure the quenching system is in place before you light the fire!