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The tolerable upper intake level (UL), or upper limit, for phosphorus is 4,000 mg a day for adults 19 to 50. That is the most a day that is unlikely to cause harm for almost everyone; above it, the chance of side effects goes up. It is a ceiling, not a target. The limit counts phosphorus from food, water and supplements together. From age 71 it is 3,000 mg; in pregnancy it is 3,500 mg.
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Phosphorus upper limits by age
| Age | Males | Females | Pregnancy | Breastfeeding |
|---|---|---|---|---|
| Birth to 6 months | Not set | Not set | – | – |
| 7-12 months | Not set | Not set | – | – |
| 1-3 years | 3,000 mg | 3,000 mg | – | – |
| 4-8 years | 3,000 mg | 3,000 mg | – | – |
| 9-13 years | 4,000 mg | 4,000 mg | – | – |
| 14-18 years | 4,000 mg | 4,000 mg | 3,500 mg | 4,000 mg |
| 19-30 years | 4,000 mg | 4,000 mg | 3,500 mg | 4,000 mg |
| 31-50 years | 4,000 mg | 4,000 mg | 3,500 mg | 4,000 mg |
| 51-70 years | 4,000 mg | 4,000 mg | – | – |
| 71+ years | 3,000 mg | 3,000 mg | – | – |
No upper limit could be set for babies; the National Academies say their intake should come from food and formula only.
How much Phosphorus you need
| Age | Males | Females | Pregnancy | Breastfeeding |
|---|---|---|---|---|
| Birth to 6 months | 100 mg* | 100 mg* | – | – |
| 7-12 months | 275 mg* | 275 mg* | – | – |
| 1-3 years | 460 mg | 460 mg | – | – |
| 4-8 years | 500 mg | 500 mg | – | – |
| 9-13 years | 1,250 mg | 1,250 mg | – | – |
| 14-18 years | 1,250 mg | 1,250 mg | 1,250 mg | 1,250 mg |
| 19-30 years | 700 mg | 700 mg | 700 mg | 700 mg |
| 31-50 years | 700 mg | 700 mg | 700 mg | 700 mg |
| 51-70 years | 700 mg | 700 mg | – | – |
| 71+ years | 700 mg | 700 mg | – | – |
* Adequate Intake (AI): the amount set when there isn’t enough evidence for an RDA.
What counts toward the Phosphorus limit
The limit counts phosphorus from food, water and supplements together.
The adult limit of 4,000 mg is 4 grams (3 grams after age 70).
What happens with too much Phosphorus
The 1997 National Academies report (Ch. 5, pp. 181-187) says "Excess phosphorus intake from any source is expressed as hyperphosphatemia". It says "The most serious, clearly harmful effect of hyperphosphatemia is calcification of nonskeletal tissues" and that, from dietary causes, this "becomes a problem mainly in patients with end-stage renal disease." The report also states that "No reports exist of untoward effects following high dietary phosphorus intakes in humans". It based the UL on the upper boundary of the normal adult range for serum inorganic phosphate.
Sources: Health Canada, Dietary Reference Intakes tables (the joint U.S.-Canada values); National Academies, Dietary Reference Intakes for Calcium and Vitamin D (2011); National Academies, Dietary Reference Intakes for Calcium, Phosphorus, Magnesium, Vitamin D, and Fluoride (1997). Limits checked November 8, 2026. More from the NIH: Office of Dietary Supplements Phosphorus fact sheet.
If you think you or a child took too much of a supplement, call Poison Control at 1-800-222-1222 (U.S., free, 24 hours) or use poison.org. In an emergency, call 911.
General information, not medical advice. Your doctor may recommend a different amount, for example to treat a deficiency. Talk to your doctor or pharmacist before you start, stop or change a supplement, especially if you are pregnant, nursing, take medication or have a medical condition.