Signs and Symptoms of Selenium Toxicity

Signs and Symptoms of Selenium Toxicity – Are you Taking Too Much?

Serious Selenium Toxicity is Rare but Minor Excess Is More Common Than you Think

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Selenium is one of the most important micronutrients in your body when it comes to your thyroid. 

Selenium also plays an important role in regulating enzymes that help protect your cells from free radicals. 

These enzymes are known as selenium-dependent enzymes (1) and they are important for many cellular pathways in your body. 

To take matters a step further, it’s not uncommon for many people to suffer from low-grade selenium deficiency

Minor deficiency is common due to rampant due to modern intensive agricultural farming methods (2) which have stripped the soil of its nutrients. 

Today this soil only contains a fraction of what it used to. 

And this soil depletion has real consequences for people like you and me when we consume fruits and vegetables. 

For these important reasons, selenium is often included in many over-the-counter supplements. 

And it is the minor toxicity that can occur from these supplements that I want to focus on today. 

You see, it’s actually quite rare that humans suffer from overt selenium toxicity. 

But it’s not uncommon for people to accidentally take too much in supplement form as they attempt to replace low levels caused by issues like soil depletion. 

And the side effects of low-grade selenium toxicity, or selenium overdose, can be difficult to identify and may actually mimic some of the same side effects as selenium deficiency. 

Another group of patients at risk for selenium toxicity is thyroid patients. 

These patients tend to take higher doses than selenium in an attempt to bring down thyroid antibodies in diseases such as Hashimoto’s thyroiditis

And while there is evidence that this can be effective, it’s also potentially harmful if the wrong dose is used. 

Let’s break it down. Today you will learn:

  • The early warning signs of selenium toxicity
  • Warning signs that you are taking too much selenium in supplement form
  • More serious side effects of selenium toxicity (these are rare)
  • How to know if you are taking the right amount of selenium and what dose you should be taking
  • And more

Let’s jump in…

Minor Problems & Symptoms (Usually from taking too much in supplement form)

While serious selenium toxicity is incredibly rare, minor selenium toxicity is not all that common. 

Selenium is found in MANY over-the-counter supplements including multivitamins, thyroid support supplements, adrenal support supplements, women’s daily vitamins, and specific selenium only supplements. 

If you aren’t paying attention, or if you are someone who is simply sensitive to selenium, it’s possible that you may be taking too much. 

It’s not too much in the sense that it will cause you serious problems but it could definitely be enough to prevent you from feeling at 100%. 

The following signs may indicate that you need to back off on your selenium dose: 

#1. Hair Loss – Selenium deficiency can also cause hair loss which means many people with hair loss use selenium. Just be sure that your dose isn’t too high or you may cause the same problem. 

#2. Brittle Nails – Selenium toxicity can cause changes to your nail beds including discoloration in your nails. 

#3. Fatigue – Fatigue and low energy may stem from thyroid problems that excess selenium may exacerbate. 

#4. Gastrointestinal (stomach) problems – This may include having an upset stomach, feeling minor stomach pains, changes in bowel movements, and so on. 

#5. Joint Pain

#6. Nausea – Nausea that sticks with you throughout the day may be an indication your selenium level is too high. 

These minor symptoms should completely fade within 2-3 months once you stop taking selenium. 

Serious problems that indicate you have Selenium Poisoning

Serious and life-threatening selenium toxicity can and does occur but is incredibly rare among humans. 

It’s much more common in livestock because the primary source of selenium depends on soil concentrations. 

If animals are consuming soil that is heavily concentrated in selenium then they may start to experience signs of excess. 

And these symptoms can also occur in adults, though it’s incredibly rare that they occur. 

Most of the time, selenium excess is typically only minor and comes from excessive use of over-the-counter supplements. 

And most people stop using the offending agent when they start to feel the minor issues listed above. 

Having said that, let’s at least mention some of the more serious side effects: 

#7. Neurological problems

#8. Paralysis

#9. Selenosis

What to do If you Experience These Signs?

The good news is that there isn’t much you need to do to “treat” the problem as it will take care of itself. 

Any extra selenium is typically eliminated from the body within 1-2 days after being consumed, provided your organs are functioning at 100%. 

But, if you do experience the warning signs of excess selenium then you should take steps to try and find the source of selenium exposure. 

This is most likely in whatever supplements you are taking but it could also be from the food you are eating or another environmental source.  

How Much Selenium Should you Take Each Day?

Well, it depends on who you ask…

The RDA for selenium is somewhere around the 40-55mcg range depending on your age (3). 

But the problem with the RDA is that it’s set for 97% of the population (which leaves out a small percentage of people), the RDA is set for only the minimum amount necessary to avoid deficiency, and it doesn’t take into account conditions where taking more may actually be beneficial. 

There’s real evidence to suggest that using the RDA is not sufficient for most people, and while it may stave off overt deficiency it’s not enough for people to thrive. 

Because of these known issues, other organizations and physicians have recommended higher doses than the 40-55mcg range. 

And while these doses are better at helping people feel better and improving symptoms, they also run a slight risk that you may take too much. 

Daily selenium intake in the 400mcg to 600mcg range has been recommended in many circles and many patients have had great success using these doses. 

In fact, studies have shown that humans can tolerate 600mcg per day for long periods of time without any issue. 

Even though the studies have shown this, I have personally seen people experience issues when consuming 600mcg per day. 

My recommendation is to stick to the 100mcg to 200mcg per day range. 

This ensures that you are supplementing with a sufficient amount to meet your body’s requirements but also not too much so that you won’t tip yourself over the edge with selenium found in your diet. 

I should point out, though, that some people see improvements in conditions like Hashimoto’s thyroiditis at higher doses. 

How to Avoid Selenium Toxicity

The best way to avoid selenium toxicity is to be vigilant about the over-the-counter supplements that you are taking day to day. 

If you are otherwise healthy, then you should always try to get as much selenium as you can from your diet. 

Selenium-rich sources of food include:

  • Brazil nuts
  • Fish
  • Ham
  • Pork
  • Beef
  • Chicken
  • Eggs
  • Brown rice
  • Oatmeal
  • Spinach
  • Bananas

If you are healthy then you may be able to get all of the selenium that you need from these sources. 

When possible, remember to try and consume organic versions of these foods as the nutrient contents are likely to be much higher (4). 

If you have a medical condition in which taking excess selenium may be beneficial, then pay close attention to how much you are taking in your supplement form and how much you may be getting from your foods. 

As long as you supplement in a low dose, in the range of 100mcg to 200mcg per day, you should not run into any issues of selenium toxicity even if you are also eating organic healthy foods high in selenium. 

People typically don’t run into issues until they hit that 600mcg per day or higher dose. 

Now I want to hear from you:

Do you think that you are taking too much selenium?

Do you have any of the signs or symptoms listed above?

How much selenium are you taking each day?

Which symptoms or side effects are you experiencing?

Leave your questions or comments below! 





warnings signs you are taking too much selenium

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About Dr. Westin Childs

Hey! I'm Westin Childs D.O. (former Osteopathic Physician). I don't practice medicine anymore and instead specialize in helping people like YOU who have thyroid problems, hormone imbalances, and weight loss resistance. I love to write and share what I've learned over the years. I also happen to formulate the best supplements on the market (well, at least in my opinion!) and I'm proud to say that over 80,000+ people have used them over the last 7 years. You can read more about my own personal health journey and why I am so passionate about what I do.

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43 thoughts on “Signs and Symptoms of Selenium Toxicity – Are you Taking Too Much?”

  1. I have noticed my nail beds are yellow and I don’t wear polish. I did have a fungus that I took a prescribed 7 day polish for but no longer use it. I am wondering if it is the daily 200 mcg Selenium. My teeth are turning yellow too Your thoughts?

  2. I got my labs today. High range is about 400 and I’m at 675. I quit taking it in august. I have stomach issues daily. Starting the feel like I have dementia. Is there anything I can do to bring my number down?

    • Hi Janet, are you feeling better now and if so how long dud it take ? I was taking a potassium supplement and after months of feeling so ill i discovered in the small print it contained selenium. I stopped supplement but 12 weeks on i still feel awful. All known symptoms and an awful metallic taste in my mouth. I hope you are better now and i look forward to a reply. Best wishes Paula from UK

  3. Dr. Childs – Is there a blood test that measures amount of selenium in as person’s body ?
    I have HAIR LOSS and FATIGUE . so, how do I know if have selenium DEFICIENCY of TOXICITY ?

    • Hi Karen,

      Unfortunately, very few nutrient tests are accurate because they typically test the serum instead of the cells which are what matter.

  4. Hi Dr Childs, I love following you & all your knowledge about the thyroid. I don’t take extra selenium, after reading your article, I’m glad I don’t! I found out about a year an a half ago that I have Hashimoto,s. I have taken Levothyroxin for 20+ years or Synthyroid….from 1.25 mg and all in between now I take .75 with a half a tablet one day a week. My labs recently were TSH .48, free T3 3.2, free T4 .89 . Back in late 2019 my Rheumatoid Factor 102, CCP Result positive, CCP Antibody 500, TPO Antibody 122…. since then I have been on Euthyrox .88 then Unithyroid .88 now Levothyroxin Sodium .75… my question is ( I know they are different forms of Levothyroxin) what makes them different? I have gut issues, dry skin, thin hair the list can go on. I’m 73 and 5 ft 1/2 in and weigh 142… I also have bloated tummy and can’t seem to lose weight. I drop 4-5 lbs and then gain it back… I’m also Diabetic A1c 5.8 take 500mg Metformin..

  5. There are a couple of scientific studies that suggest that even 200 ug/d is too much for some people. That dosage seems to have contributed to cognitive problems for my wife. 100 ug/d should be sufficient for anybody. 600 ug/d might be a short term medical treatment, but would be insane as a supplement.

  6. Hi Dr,
    Would ringing in the ears be a possible symptom of too much Selenium?
    I take 200 mcg of L-selenomethionine a day. vital signs stable, weight is 104 pounds.
    Really appreciate your knowledge!

  7. This is terrifying. I’ve discovered Brazil nuts a month ago and because they are low carb I’ve eaten 30 nuts daily even more. For At least a month. Garlic breath and regularity for sure are symptoms. Please help me how to reverse any damage! They are in trash but what can I do in meantime if anything? Wait it out?

  8. Hi Dr. Child’s,
    I knew you would have the answer for this . My selenium RBC was slightly elevated 323 (range 120-300). I had prob had the gastro symptoms for a month with nausea all day but didn’t correlate it with the selenium . I only supplement about 150-200mcg/day but I had been consuming oatmeal daily + fish and shrimp. I also have the MTHFR genetic mutation which I don’t know if that makes a difference . Can excess selenium also cause lightheadedness and vertigo? I had to go ER for vertigo and all they found was high free t3 (4.1 , which is top of the range )and the selenium. Also, how fast can this exit the body? I had been feeling great and my Hashimoto’s antibodies are nearly in remission but I’m feeling pretty cruddy with this selenium business . Thanks for your help

    • Hi Kim,

      Excess selenium typically doesn’t cause those symptoms but it’s always possible. If you stop taking selenium it should be out of your body fairly quickly, within days.

  9. Hi

    I just accidentally took like 50 drops rather than 4 of my Selenium making that about 3000 mcg of Selenium I would guess. Will I have toxicity or die? Or serious side effects from one overdose?

  10. I have Hashimoto’s, and take 75 Cg of level thyroxine. At my endocrinologist Office I was a little hyper so now I take that only for five days not seven. At the time my symptoms were anxiety, nausea, brain fog, low energy, I always had the nails and I wear a hippie so I don’t know about that. Anyway I was taking selenium 200 every day as suggested. When my endocrinologist checked my selenium levels they were 265 that was on 8/26/ 2021. I stopped taking them that day and took another blood test October 5, 2021, it was 385. I’ve been feeling anxious, no energy, definitely neurological issues, stomach pain, and bathroom issues. But I also have dysautonomia, EDS, mast cell Disorder, MALS,Undifferenated Connective Tissue Disorder, Sjogren’s, small fiber neuropathy, fibromyalgia, IBS, GER de, and a few other things I probably forgot without a doubt. I don’t know what excessive high amounts of selenium 385 To meters high but what do I know can you suggest anything? Thank you

  11. Hi I took a blood test two weeks ago and today I was surprised to find out my selenium levels are too high…241. No more selenium for me in the upcoming weeks. I was wondering why I’m having so much pain, nails are weaker than usual and talk about gassiness. Embarassing. I’ve been taking Selenomethione 200 mcg. for about 7 or 8 months. I think in the beginning it was really helping me, my energy was really good but now I’m very tired.

    • Hi Deborah,

      You may want to check your food sources of selenium. Usually, a dose of 200mcg should not lead to elevated selenium unless you are getting extra from other sources.

    • Hi Jim,

      No, 1 brazil nut will most likely not be too much unless you are getting high doses of selenium from another source as well.

  12. Hi Dr Childs,
    I’m taking anywhere between 250 and 325. I have hair loss, brain fog, dizziness, lightheadedness, some fatigue, sore joints (knees and fingers). I’m 5 foot 2 inches and weigh 135 pounds so not heavy. I’ve been eating 10g of brazil nuts per day for the past 4 to 5 months. I also eat oats almost every day as well as chicken, and beef. I eat vegetarian two days per week. I’m wondering if my symptoms may be related to selenium toxicity. Thanks in advance!

    • Hi Jo-Anne,

      The best thing you can do is to take an estimated stock of how much selenium you are consuming from ALL sources and then compare that to the recommended levels in posted in this article. It’s hard to know where your symptoms are coming from without more information.

  13. Hi. I want to say how fantastic it is to read well written but non simplified RDA type bullshit. No one size fits all in your article. Very clear. Aam almost gonna become a carnivore diet coach I think. Saving your article.
    My question:
    I’m trying to find an iodine literate doc in town. Mine doesn’t even countanance giving labs I want that he doesn’t understand. I’ve been eating carnivor-ish/keto so shouldn’t be deficient in selenium but also started taking iodine up to about 20mg following doc browns book. Forgot to take selenium but took the other pre supplements, magnesium, b vits, but C – used a lemon a day.y question now is if my doctor won’t give me labs do I continue the iodine cos I’m up to that dose. Felt a bit weird the other day so missed/pulsed a dose off that day. Should I decrease the iodine dose and eat four Brazil nuts to make sure every other day? On a himpurus note I’d love my hiar to come back. Do you give advice as a doc for payment. I can’t afford much but offer that for help. Stuck in a small town by docs over loaded by patient load and mine’s lost his spark and its hard to change to another.

    • Hi Aidan,

      I’m actually not a huge fan of high-dose iodine for the reasons listed here:

      There are some people who do exceptionally well with higher doses of iodine (in the range you are taking) but there are plenty who experience serious side effects up to and including the onset of autoimmune disease. As a result, I don’t think the benefits outweigh the potential cons for most people and because there are other much safer natural therapies, it doesn’t usually make sense to push high dose iodine so hard:

      I’m not seeing patients or doing consults at this time but if that ever changes I will send out an email to my mailing list!

  14. Hi, Dr. Childs! I do not take selenium, but it is elevated (June 28-464 mcg/L and July 30 – 473 mcg/L). There is selenium in my prenatal vitamin (I had a baby 3 months ago), but I have been taking that since before I was pregnant. The only other medications I take are levothyroxine and liothyronine. I don’t eat much of the foods high in selenium.
    Any ideas what could be causing elevated selenium? I also have elevated zinc (June 28 – 15.69 mg/L, July 30 – 16.63 mg/L).

    • Hi Gretchen,

      Unfortunately, many of the tests that we have for nutrient deficiencies are very inaccurate. They only tell you how much of that nutrient is in the blood (typically) but fail to provide information about cellular concentration or how well it is being utilized for the body. It’s hard to take blood levels and make general statements about the entire body with that type of limited information.

  15. I take 200mcg per day and I eat a vegan diet. I have had an increase in hair loss as well as nausea. My nails are fantastic, better than ever. So I have no idea! I have other reasons why hair loss might be happening as I am hypothyroid and am on levothyroxine, I also have lower ferritin levels and maybe need more zinc? Not sure.

  16. Hello there. I have Hashimotos and have taken selenium daily for few years. When I first started selenium supplimentation in 2018 I took 300 per day but lowered it to 150 after year and stayed there. Last week a blood test confirmed my best tpo and tg antibody counts and thyroid function in 17 years. I now also take LDN. The test also showed high selenium levels at 3.4. My doctor told me to have a break from it for a month to lower it. By day four I was tired and a little sore. By day five of no selenium I was exusted, breathless and terribly achey. So last night I halved my selenium into an empty capsule to make it 75 and this morning I woke feeling ok. Is it possible for my body to feel the lack of selenium this quickly? Is it some sort oc detox effect? Was my high selenium reading just selenium circulating in yhe blood and not nessesarily stored selenium? P.s I dont eat brazil nuts and my other suppliments do not contain selenium.

  17. Hi Dr Childs,

    I tested recently and my selenium levels came out as quite high at 222 ug/l. This was after taking 200mcg selenium daily for four weeks alongside iodine to remedy an iodine deficiency (2 x 12.5mg for two weeks, 1 x 12.5mg for two weeks).

    Ironically, my iodine deficiency worsened: from 90ug/l in urine test before supplementation to 50ug/l after supplementation. Is there a relation between selenium toxicity and iodine deficiency?

    Thank you!

  18. Dr. Childs,

    I understand serum testing is inaccurate, but what about Selenium RBC? I did this test awhile back and my reading was 487 (range 120-300). I had been taking probably 200mcg daily for a year. I have since stopped for many months now (even though I didn’t notice toxicity symptoms). Not sure if I should start taking it again or not? I have Hashimoto’s, so I’m trying to keep that in check. Should I test again first, or is the test worthless?

    • Hi Diana,

      It wouldn’t be an accurate way to assess total body selenium, but it would have some merit in assessing the selenium content in the blood. I personally wouldn’t recommend using it as a way to determine your selenium dose but there are some who think differently than me on that topic.

  19. Dr Childs,

    After taking a selenium supplement for several months I starting experiencing hair loss. I micronutrient blood test showed my selenium level high at 404 (120-200 mcg/L). I have checked all of my supplements and stopped taking any containing selenium for about 3 weeks now. How long will it take for the selenium level to right itself and the hair loss to stop? Will the hair grow back? This is extremely stressful…

    I also want to lower selenium intake in my diet. It appears all meat/fish/poultry contain high levels of selenium. Which would be the best choices? Are there any fish varieties that are lower in selenium? I am not finding any information on what I should be eating to help correct this.

    Is there anything else you recommend doing to help lower selenium levels? Any information would be greatly appreciated.

    Thank you,

    • Hi Linda,

      The body will metabolism the excess selenium on its own so as long as you don’t put any more into the system you should be fine.

  20. Hi Dr. Childs.
    I had recently added Brazil nuts to my mixed nut daily regime. What I didn’t realize is the amount of selenium each nut contains. Amazed that it is not required to be on the Brazil Nut packaging. I ended eating approximately 400 nuts in 1 month. The amount of selenium in the Brazil nuts along with a multivitamin put me at approximately 41,000 micrograms of selenium in 30 days This doesn’t take into account other foods. That amount is way over the RDA & tolerable upper intake level.
    Safe to say digestive issues set in but I was also diagnosed with pancreatic insufficiency. Do you think the toxic levels of selenium could be the cause.

  21. After dealing with Hashimotos for a few years now, I have just had to experiment as there seems to be no answers and so much conflicting info. I needed iodine as it fixed all hormone dysfunction but caused extreme burning/raw of the thyroid causing a flare. Even recommended daily iodine amounts would cause this. I have decided to be brave and try 200mcg selenium first for a month. Then started titrating up with mcg amounts of iodine. The selenium is working. No more thyroid burning. With 200mcg of selenium, I was on the border of thyroid pain/burning so I discovered that raising the selenium to 450mcg a day took all the pain/burning away! I am raising the iodine to high mcg levels and having absolutely no problems for the first time, since Hashimotos, taking iodine.

  22. Dr. Childs,

    You write, “Minor deficiency is common due to rampant due to modern intensive agricultural farming methods (2) which have stripped the soil of its nutrients. ”

    It sounds like you’re on a soapbox. Do a quick search for which areas of the country have different selenium levels, and you’ll realize there is lots of natural variation. ( as an example.) As a livestock veterinarian, we have to take into account these variations, even within a relatively small area sometimes. We also have to account for the fact that some plants accumulate selenium at greater rates than other plants leading to potential toxicity in livestock grazing those plants.

    Unless you have some definitive proof of how Se is depleted by modern agricultural processes, or even a hypothesis of how this process works, then please don’t pontificate on this and mislead people.

    • Hi Stephan,

      This blog is the very place that I write, pontificate, and theorize, to encourage conversation. I would say this is pretty standard for this type of blog.

      In regards to your comments, I’m aware of the variations in selenium levels in soil and the various rates at which selenium is taken up by plants which is discussed more in this article:

      I’m also aware that much of the information we have on selenium toxicity is from animals and livestock which is helpful as a model for humans.

      But I’m not sure why it matters if modern farming is partially responsible for the variations in selenium concentrations in soil or not as this doesn’t really impact the overall message of this article which is about selenium toxicity from the use of supplements.

      I’m only attempting to account for what I see clinically which is that many people people benefit from taking additional selenium. I’m guessing that at least part of this can be explained by the selenium content in foods which is likely impacted by a combination of factors including soil variation by region and other factors like modern farming techniques.

  23. Are there any heatlh condition that would result in slightly elevated selenium?

    My selenium has always at the very top of referance range, occasionally going a few points over.

    This pattern has been consistant over the last 7 years despite changes in diet, lifestyle, & thyroid function (hypothyroid & on full thyroid replacement for 7 years, in last 6 months regained full thyroid function & now off thyroid medication).

    Wondering if issues related to liver metabolism, particularily methylation & related metabolic processes?

    My thyroid regained full function after starting high dose (21 grams daily taken as multiple doses) Betaine TMG therapy to treat resistant elevated homocysteine levels. Had always assumed related to MTFHR mutation even though levels did not respond to different forms of B12 (methyl& hydroxy).

    Used to have chronic slightly elevated/top of range B12 levels which responded to lowering of homocysteine levels via high dose Betaine TMG supplementation. Thyroid regained full function around this same time period.

    Wondering if elevations in certain vitamins & antioxidents could represent problems in methylation & related processes. For example lack of methyl donors could result in decreased methylation with possible accummulation of ‘unused’ vitamins & antioxidents? Much in the same way insulin resistance & other metabolic issues result in elevated serum glucose levels due to decreased cellular uptake?


  24. Hello Dr. Child’s, l started eating 3 Brazil nuts this week and then switched to two 100 mcg selenium today. My body temperature was 34.5 degrees celsius at my doctors appointment. My naturopath doctor advised me take one Brazil nut if my body temperature dropped again.. My body temperature went up to 36.0 degrees celsius within an hour. I noticed my muscles became sore. Is this a symptom that l took too much selenium? In total, l took 200 mcg plus the one Brazil nut today. I’m concerned about overdosing on selenium. Is my low body temperature the result of low deficiency of selenium? I would greatly appreciate your expertise. Thank you, Don

  25. Hi There~
    I just received results from a comprehensive hair test. Any idea why I might have 400x higher than normal selenium and I do not take selenium? (And so far no signs of dementia) I have some minor symptoms like brittle nails and maybe some hair loss and have been in remission as a thyroid patient (Graves’s ) and my thyroid looks pretty perfect but the TPO is also out of control at 902. EEK! Curious, Kate

  26. I ate 20 Brazil nuts didn’t know about the high selenium content of these
    Nuts they were shelled and easy to eat to many,whats my prognosis
    Should I be worried it’s been 5 days.i have a ringing in my ears and metallic taste has gone away.


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