If you are asking how much selenium to take for thyroid support, the short answer most practitioners land on is 200 micrograms (mcg) per day for adults using a supplement, taken with food. The government's baseline requirement is far lower, about 55 mcg a day, but many people focused on thyroid support choose a higher, still-safe daily amount in the 100 to 200 mcg range. The ceiling matters too: staying at or under 400 mcg a day from all sources keeps you well inside safe territory. Below, we walk through why that number comes up so often, how to read it against your own diet, and how to take selenium without overdoing it.
In this article
- How much selenium should you take per day?
- Why is selenium tied to the thyroid?
- Can you get enough selenium from food?
- What are the signs of low selenium?
- Can you take too much selenium?
- Frequently asked questions
How much selenium should you take per day?
The recommended dietary allowance for selenium is 55 mcg a day for most adults, and 60 to 70 mcg during pregnancy and breastfeeding. That is the amount needed to cover basic requirements in a healthy person. When people talk about selenium specifically in the context of thyroid support, the number they reach for is usually higher, most often 200 mcg a day, because that is the dose used in much of the published research on selenium and thyroid function.
Here is a simple way to think about the range for adults:
| Daily amount | What it represents |
|---|---|
| 55 mcg | Baseline daily requirement for most adults (RDA) |
| 100 to 200 mcg | Common range chosen for thyroid support with a supplement |
| 400 mcg | Upper safe limit from all sources combined (do not exceed) |
A few practical notes. Selenium is best taken with food, and the form called selenomethionine is the one most often used in supplements because the body absorbs it well. If you already eat a selenium-rich diet, you may not need the full 200 mcg from a supplement. And if you have a thyroid condition or take thyroid medication, the right number for you is a conversation with your own practitioner, not a blog. Bring the question to them directly.
200 mcg of selenium in easy liquid drops, to help support healthy thyroid function and your body's natural antioxidant defenses.
Why is selenium tied to the thyroid?
Your thyroid holds more selenium per gram of tissue than any other organ in the body, and there is a good reason for that. The enzymes that help your body convert thyroid hormone into its active form, and the antioxidant enzymes that protect the thyroid gland from everyday oxidative stress, are built using selenium. In plain terms, the thyroid needs selenium to do its ordinary daily work.
This is why selenium and iodine are often discussed together. They work as a pair, and being low in one can throw off how your body handles the other. Selenium supports the machinery; it is not a switch that flips your thyroid on. If your thyroid feels off, selenium is one supportive piece of a bigger picture, and worth looking at alongside a proper workup with your practitioner rather than on its own.
Researchers have studied selenium closely in people with thyroid conditions, and reviews of that work point to a real role for the mineral in normal thyroid function. If you want to read the underlying science, the National Institutes of Health keeps a plain-language fact sheet that is a good starting point.
Can you get enough selenium from food?
Often, yes. Selenium is present in a lot of everyday foods, and many people meet their baseline needs without thinking about it. The richest source by far is the Brazil nut. A single Brazil nut can carry roughly 68 to 91 mcg of selenium, which means one or two a day can cover a lot of ground. Other good sources include seafood, eggs, poultry, and whole grains.
The catch with Brazil nuts is consistency. The selenium content of a Brazil nut depends on the soil the tree grew in, so it can swing widely from nut to nut, even within the same bag. That makes it hard to know whether you are getting 20 mcg or 90 mcg on any given day. For casual topping up, a couple of Brazil nuts is a lovely, whole-food option. When you want a steady, known amount every day, a measured supplement takes the guesswork out. For a full breakdown, see our comparison of Brazil nuts vs a selenium supplement.
Unlike a handful of Brazil nuts, each serving of Go Nutrients Selenium gives you the same measured amount, in drops you can add to water.
What are the signs of low selenium?
True selenium deficiency is uncommon in places with selenium-rich soil, but lower-than-ideal levels do happen, especially with certain diets or digestive conditions. The signs are broad and easy to blame on other things, which is part of why they get missed. Commonly discussed signs of low selenium include:
- Ongoing tiredness and low energy
- Thinning hair or more hair shedding than usual
- Brittle nails, sometimes with white spots
- Getting sick more easily than you used to
- A general foggy, run-down feeling
None of these on their own means you are low in selenium, and the honest move is to get it checked rather than guess. If this list sounds familiar and you have been told everything is "normal," you are not imagining it, and it is reasonable to keep asking questions until you feel heard. For a closer look, see the 7 signs of low selenium.
Can you take too much selenium?
Yes, and this is the one to respect. Selenium has a relatively narrow window between "enough" and "too much." The upper limit for adults is 400 mcg a day from food and supplements combined. Regularly going well above that can lead to a condition called selenosis, whose signs include a garlic smell on the breath, a metallic taste, hair or nail changes, and stomach upset.
The practical takeaway is simple: a 200 mcg daily supplement sits comfortably within the safe range for most adults, but stacking several selenium products, or adding a big daily habit of Brazil nuts on top, is how people accidentally push past the ceiling. Pick one reliable source, know its amount, and you stay in the safe zone.
Frequently asked questions
How much selenium should I take for thyroid support?
Most people focused on thyroid support use a supplement in the 100 to 200 mcg per day range, with 200 mcg being the most commonly cited amount in the research. The baseline requirement for general health is 55 mcg a day. Do not exceed 400 mcg a day from all sources, and check with your practitioner if you have a thyroid condition or take thyroid medication.
When is the best time to take selenium?
Selenium is generally taken once a day, with food, to support absorption and to be gentle on the stomach. The time of day matters less than taking it consistently.
Can I take selenium with my thyroid medication?
Many people do, but timing and dosing should be worked out with the practitioner who manages your thyroid medication, since some supplements and thyroid medications are taken at different times of day. Ask them before adding it.
Is it better to eat Brazil nuts or take a selenium supplement?
Both can raise selenium levels. Brazil nuts are a great whole-food source but vary a lot in how much selenium they actually contain, so the amount you get is unpredictable. A supplement gives you the same measured amount every day, which is easier to track against the safe upper limit.
How long does selenium take to work?
Selenium is a nutrient your body uses continuously rather than a quick fix, so think in terms of steady daily intake over weeks and months, not days. Consistency is what matters.
A simple, steady 200 mcg
Go Nutrients Selenium gives you a known daily amount to help support healthy thyroid function and your body's antioxidant defenses, in easy liquid drops.
Shop Go Nutrients Selenium →These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease. This article is for education and is not medical advice.