Selenium Dosage: Daily Needs by Age and 50 vs 200 mcg Compared
How Much Selenium Do You Need Each Day?
With selenium, the gap between a helpful amount and a harmful one is relatively narrow. That makes getting the selenium dosage right more important than simply buying a supplement. This guide sets out the daily requirement for every age in a table, the safe upper limit, and the practical difference between 50 mcg and 200 mcg capsules.
Recommended Selenium Dosage by Age
The table below shows the Recommended Dietary Allowance and the Tolerable Upper Intake Level, which covers food and supplements together, according to the NIH Office of Dietary Supplements:
| Age group | RDA | Upper limit (UL) |
|---|---|---|
| Birth to 6 months | 15 mcg | 45 mcg |
| 7 to 12 months | 20 mcg | 60 mcg |
| 1 to 3 years | 20 mcg | 90 mcg |
| 4 to 8 years | 30 mcg | 150 mcg |
| 9 to 13 years | 40 mcg | 280 mcg |
| 14 years and over | 55 mcg | 400 mcg |
| Pregnancy | 60 mcg | 400 mcg |
| Breastfeeding | 70 mcg | 400 mcg |
The supplements mentioned here are for adults only and should not be given to children unless a doctor prescribes them.
Where Your Daily Selenium Comes From
Most people meet their selenium dosage needs through food: fish, eggs, poultry, meat and grains. A single Brazil nut can exceed 100 mcg, close to twice the adult requirement, so go easy on them if you also take a supplement, or your total selenium dosage may climb fast. Selenium content in grains varies widely with the soil they were grown in, which is why intake differs between countries.
Selenium Dosage Compared: 50 mcg vs 200 mcg
| Product | Strength | Source and capsule | Directions |
|---|---|---|---|
| Solaray Selenium 50 mcg | 50 mcg (91% DV) | Selenium yeast, gelatin capsule | 1 capsule daily with a meal or glass of water |
| NOW Selenium 200 mcg | 200 mcg (364% DV) | L-selenomethionine, yeast free, veg capsule | 1 capsule daily with a meal |
| Solaray Selenium 200 mcg | 200 mcg (364% DV) | L-selenomethionine, yeast free, VegCap | 1 VegCap daily with a meal or glass of water |
As a selenium dosage, the 50 mcg capsule sits close to the daily requirement, so it suits people who want light support for a poor diet and keeps total intake far below the upper limit. The 200 mcg capsule is the dose used in Hashimoto’s trials and is usually taken for a defined period under medical supervision. A 200 mcg supplement plus an ordinary diet normally stays under 400 mcg, but the margin narrows with Brazil nuts or a multivitamin.
When Is a Higher Selenium Dosage Used?
This higher selenium dosage has two main uses. In Hashimoto’s thyroiditis, some trials found that 200 mcg of selenomethionine lowered TPO antibodies, without evidence that it changes the hormone dose, so never stop levothyroxine. In mild Graves’ eye disease, European guidance supports selenium for about 6 months. The details are in our article on selenium and thyroid health.
Tips for Taking Selenium Safely
- Take your selenium dosage with a meal to reduce stomach upset.
- Do not combine two products that both contain selenium.
- Count the selenium in your multivitamin toward the total.
- Ask your doctor during pregnancy or breastfeeding, with kidney disease, or during chemotherapy.
- People living in areas with high soil selenium should consult a doctor first.
Signs Your Selenium Dosage Is Too High
Taking more than 400 mcg a day for a long time can cause selenosis. Warning signs include garlic breath, a metallic taste, hair loss, brittle or discoloured nails, skin rash, diarrhoea, fatigue and irritability. If these appear, stop the supplement and see your doctor. The SELECT trial also linked years of 200 mcg a day with a possible higher risk of type 2 diabetes, with no protection against cancer.
A blood selenium test is not part of routine checkups; doctors order it when deficiency or toxicity is suspected. If you are having other blood work, our article on biotin and lab tests explains how supplements can affect results.
Frequently Asked Questions About Selenium Dosage
Should I take selenium in the morning or evening?
Timing of the selenium dosage matters little; what matters is taking it with a meal and consistently.
Is 200 mcg too much?
It is below the upper limit but more than 3 times the requirement, so do not take it long term without a reason.
Are these capsules suitable for vegetarians?
The NOW and Solaray 200 mcg capsules are vegetarian; the Solaray 50 mcg capsule is gelatin.
Can I split a 200 mcg dose?
Capsules are not designed to be split. If you need a lower amount, the 50 mcg product is the simpler choice.
Conclusion
The adult selenium dosage is 55 mcg a day, rising to 60 mcg in pregnancy and 70 mcg while breastfeeding, with an upper limit of 400 mcg from all sources. To understand what the mineral does, read selenium benefits, then choose between 50 and 200 mcg with your pharmacist’s help.
This article was reviewed by the No Style Like pharmacy content team. It is for general awareness only and does not replace advice from your doctor or pharmacist.
Do not exceed 400 mcg of selenium a day from food and supplements combined, and ask a doctor before giving any supplement to children. For more information see the NIH Office of Dietary Supplements selenium fact sheet.