Calcium: How Much Is Too Much? The UK Upper Limit Explained

How much calcium is too much?

For most UK adults the daily target is about 700mg, and the risk of "too much" comes almost entirely from supplements — not from food. The NHS, the Royal Osteoporosis Society and the National Osteoporosis Guideline Group all set the reference nutrient intake for adults aged 19 and over at 700mg a day, and all three say most people can reach it through a varied, balanced diet.

NHS, Calcium — Vitamins and minerals, 2026

Where problems creep in is with supplements and fortified foods, which can push your total well past what your body needs. Calcium is essential for bones — but with this mineral, more is not better once you are meeting your target. If you are weighing up whether you need a supplement at all, our companion guide on whether you need calcium supplements walks through who genuinely benefits.

What is the safe upper limit for calcium supplements?

The NHS states that taking 1,500mg or less a day of calcium from supplements is unlikely to cause any harm — above that, it warns of stomach pain and diarrhoea. The Royal Osteoporosis Society uses the same 1,500mg supplement threshold and adds that going over it can also lead to kidney stones and constipation.

Royal Osteoporosis Society, Calcium, 2026

Two things are worth underlining. First, 1,500mg is a supplement figure, not a limit on the calcium in your dinner. Second, because several products stack calcium — a supplement, a fortified plant milk, fortified breakfast cereal, indigestion remedies — it is easy to reach a high total without noticing. Reading labels and adding up your sources is the practical safeguard.

What happens if you take too much calcium?

In the short term, too much calcium from supplements tends to upset the gut. The NHS notes that supplement doses above 1,500mg a day can cause stomach pain and diarrhoea, and the Royal Osteoporosis Society adds that going over that level can also lead to kidney stones and constipation over time.

A separate, more serious concept is hypercalcaemia — too much calcium in the blood. This can cause excessive thirst, needing to pass urine often, nausea, constipation, tiredness, muscle weakness and, when marked, confusion. Importantly, persistently high blood calcium is usually driven by an underlying medical condition — most often overactive parathyroid glands — rather than by a normal diet. A sensible calcium intake does not "tip" a healthy person into hypercalcaemia, but ongoing symptoms like these are a reason to see your GP for a simple blood test.

On kidney stones, the strongest single piece of evidence comes from the Women's Health Initiative, a large randomised trial. Postmenopausal women given 1,000mg of calcium plus vitamin D each day had a modest but statistically significant increase in kidney stones compared with those given a placebo.

Jackson RD et al., Calcium plus Vitamin D Supplementation and the Risk of Fractures, New England Journal of Medicine, 2006

Notably, dietary calcium is not linked to the same stone risk — another reason UK guidance leans on food first.

Do high-dose calcium supplements harm the heart?

This is one of the genuinely unresolved questions in bone nutrition, and it is fair to present both sides. On one hand, a 2021 meta-analysis of clinical trials found that calcium supplements — not calcium from food — were associated with roughly a 15% higher risk of cardiovascular disease, in a population that was overwhelmingly postmenopausal women. The proposed mechanism is that a large supplement dose briefly raises blood calcium in a way that food, absorbed slowly, does not.

Myung SK et al., Calcium Supplements and Risk of Cardiovascular Disease: A Meta-Analysis of Clinical Trials, Nutrients, 2021

On the other hand, a 2016 clinical guideline reviewing the same field concluded that calcium — from food or supplements, taken within the tolerable upper intake level — has no established relationship with cardiovascular disease in generally healthy adults.

Kopecky SL et al., Lack of Evidence Linking Calcium With or Without Vitamin D Supplementation to Cardiovascular Disease in Generally Healthy Adults: A Clinical Guideline, Annals of Internal Medicine, 2016

The honest summary: the evidence is mixed and the signal, where it appears, is specific to supplements and modest in size. The pragmatic takeaway is not to fear calcium, but to avoid mega-dosing — aim to reach your daily target rather than blow past it, and get the bulk of it from food.

Who should be cautious with calcium supplements?

Some people should be more careful than the general 1,500mg figure suggests, and should take supplements only on medical advice. That includes anyone who has had kidney stones, who has a history of hypercalcaemia or overactive parathyroid glands, who has a condition such as sarcoidosis, or who is already taking high-dose vitamin D (which increases how much calcium you absorb). If you take an osteoporosis medicine or several fortified products, it is also worth totting up your total intake with a pharmacist or GP.

Calcium never works alone, either. Vitamin D governs how well you absorb it, and other nutrients support the wider picture — our guides on vitamin D, calcium and protein for bone health and magnesium and bone health put calcium in that fuller context. The goal is balance, not maximisation.

Should you worry about getting too much calcium from your meals?

For nearly everyone, no. The upper-limit warnings, the kidney-stone signal and the heart debate all cluster around high-dose supplements. Calcium from a varied diet — dairy or fortified alternatives, tinned fish with the bones, leafy greens, bread and fortified flour — is absorbed gradually and is very hard to overdo. UK guidance is consistent that food is the preferred route, and that reaching roughly 700mg a day from meals is the target most people should aim for.

Know your bones before you supplement

If you are taking calcium because you are worried about osteoporosis, it is worth knowing where your bone health actually stands before you reach for high-dose supplements. Screen My Bones uses REMS — a radiation-free, ultrasound-based bone scan — to assess bone strength without X-rays, so a check can be repeated as often as needed to track change over time. You can learn how REMS technology works, read about our bone health assessment, or book an assessment to get a clear baseline. A measured picture of your bones is a far better guide to what your body needs than guessing with supplements.

This article is general information, not medical advice. Always speak to your GP or pharmacist before starting or increasing a calcium supplement, particularly if you take other medicines or have a kidney, parathyroid or heart condition.