Short answer: The NIH Office of Dietary Supplements lists a recommended daily magnesium intake of 400 to 420 mg for adult men and 310 to 320 mg for adult women, counting food, drinks, supplements, and medicines together. The separate upper limit for supplements and medicines is 350 mg a day for everyone age 9 and older.
Recommended daily amounts by age
These figures come from the Food and Nutrition Board at the National Academies of Sciences, Engineering, and Medicine and are summarized by the NIH. They are Recommended Dietary Allowances (RDAs), except for infants, where they are Adequate Intakes (AIs) because there was not enough evidence to set an RDA. Amounts are in milligrams (mg) per day and cover magnesium from all sources.
| Age | Male | Female | Pregnancy | Lactation |
|---|---|---|---|---|
| 0–6 months | 30 mg (AI) | 30 mg (AI) | — | — |
| 7–12 months | 75 mg (AI) | 75 mg (AI) | — | — |
| 1–3 years | 80 mg | 80 mg | — | — |
| 4–8 years | 130 mg | 130 mg | — | — |
| 9–13 years | 240 mg | 240 mg | — | — |
| 14–18 years | 410 mg | 360 mg | 400 mg | 360 mg |
| 19–30 years | 400 mg | 310 mg | 350 mg | 310 mg |
| 31–50 years | 420 mg | 320 mg | 360 mg | 320 mg |
| 51+ years | 420 mg | 320 mg | — | — |
If you are pregnant, breastfeeding, or shopping for a child, ask a doctor or pharmacist before using any supplement.
What counts toward your daily amount
The amounts above include magnesium from everything you eat and drink, plus supplements and some medicines. The NIH notes that magnesium is naturally present in many foods, is added to some food products, is sold as a dietary supplement, and is found in some medicines such as antacids and laxatives. In general, about 30% to 40% of the magnesium in food and beverages is absorbed by the body.* Water counts too, and the amount varies widely, from about 1 mg to more than 120 mg per liter depending on the source.
How to read “% Daily Value” on a label
Nutrition and Supplement Facts labels show a Daily Value (DV) so you can compare products. The FDA sets the Daily Value for magnesium at 420 mg. The NIH considers a food that provides 20% or more of the DV to be a high source. For example, one ounce of roasted pumpkin seeds provides 156 mg, which is 37% of the DV. Our guide to magnesium in everyday foods lists more.
The upper limit for supplements
The Tolerable Upper Intake Level (UL) is the highest daily amount that is unlikely to cause harm for most people. For magnesium, it applies only to magnesium from supplements and medicines. It does not include magnesium that occurs naturally in food and beverages.
| Age | Upper limit from supplements and medicines |
|---|---|
| Birth–12 months | None established |
| 1–3 years | 65 mg per day |
| 4–8 years | 110 mg per day |
| 9 years and older, including pregnancy and lactation | 350 mg per day |
The NIH says high doses of magnesium from supplements or medicines can cause diarrhea, nausea, and abdominal cramping, and that very high doses can be dangerous. Our guide to magnesium supplement safety and interactions covers this in more detail.
Are most people getting enough from food?
The NIH reports that many people in the United States consume less than the recommended amounts of magnesium, with men age 71 and older and adolescent males and females at the highest risk of low intakes. It also says that nutritional needs should be met primarily through the diet, and that dietary supplements may be useful when it is not possible to meet the needs for specific nutrients through food alone.*
Comparing a product to these numbers
Labels do not always list magnesium the same way. Some list the amount of the whole ingredient, such as magnesium citrate, and others list the amount of magnesium that ingredient provides. If you are comparing a product with the daily amounts and upper limits on this page, read the Supplement Facts panel and the directions carefully, and ask a pharmacist or doctor if anything is unclear.
Where PhiNaturals Magnesium Citrate fits
PhiNaturals Magnesium Citrate capsules are made with 400 mg magnesium citrate, cellulose, and a vegetable capsule shell (HPMC), and are packaged in the USA in a GMP facility. Follow the directions on the bottle, and check with a doctor or pharmacist first if you are pregnant, nursing, or taking medicines. See the product page.
Sources
- NIH Office of Dietary Supplements. Magnesium: Fact Sheet for Health Professionals (updated January 6, 2026).
- NIH Office of Dietary Supplements. Magnesium: Fact Sheet for Consumers (updated March 22, 2021).
- U.S. Food and Drug Administration. Daily Value on the Nutrition and Supplement Facts Labels (current as of March 5, 2024).
Written by the PhiNaturals team. Sources reviewed October 30, 2026. This article is for general education and is not medical advice.
*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.