High calcium, PTH and mineral metabolism

Blood test to investigate high or low calcium with intact PTH, total and albumin-corrected calcium, phosphorus, magnesium, vitamin D, kidney function and 24-hour urine calcium. It assesses mineral metabolism and helps indicate whether there is a parathyroid problem, a kidney disorder or an imbalance related to vitamin D or magnesium.

No prescription or appointment needed

Results in 1-2 working days

Blood and 24-hour urine sample. Includes: Intact PTH · Total calcium · Albumin · Albumin-corrected calcium · Magnesium · Phosphorus · Vitamin D · Creatinine and eGFR. 10 in total. See what each one measures

What it is for

It is used to investigate abnormal calcium and check whether PTH responds as it should. With high calcium, a raised or inappropriately normal PTH can point towards primary hyperparathyroidism. With low calcium, magnesium, vitamin D, phosphorus and kidney function help explain the pattern.

The 24-hour urine adds information about calcium excretion and may be needed to distinguish hyperparathyroidism from other inherited causes of hypercalcaemia, as well as providing context in people with kidney stones.

When it is recommended

High or low calcium in a previous blood test
Raised PTH or a mismatch between calcium and PTH
Recurrent kidney stones or high urine calcium
Early, severe or unexplained osteoporosis
Low vitamin D with raised PTH or a poor response to supplements
Cramps, tingling or weakness together with abnormal calcium

Clinical comment

Total calcium depends on albumin. The corrected calculation helps when albumin is abnormal, but it is still an approximation. If the result does not fit the clinical picture, ionised calcium can be a more direct measurement and should be requested separately.

PTH is not simply classified as high or low. With hypercalcaemia it should be suppressed, so a value within the range may be inappropriately normal and point towards a parathyroid cause. It is that relationship between calcium and PTH that matters.

We have included magnesium because a significant deficiency can reduce PTH secretion and lessen the response of the tissues. Phosphorus, vitamin D and kidney function are also included because any of them can change the pattern.

The 24-hour urine is only useful if the collection is complete. Missing one void, or collecting for more or less than 24 hours, can change urine calcium and clearance to the point where they are difficult to interpret.

Dr. Antonio Mas

What is tested

Intact PTH: The parathyroid hormone that regulates calcium and phosphorus. It is always interpreted together with calcium.
Total calcium: Measures circulating calcium, both bound and not bound to proteins.
Albumin: The main protein that calcium binds to, used to estimate corrected calcium.
Albumin-corrected calcium (calculated): Relates blood and urine calcium to help distinguish between causes of hypercalcaemia.
Magnesium: A significant deficiency can alter the secretion and action of PTH.
Phosphorus: Helps recognise the pattern of hyperparathyroidism and other disorders of mineral metabolism.
Vitamin D (25-OH): Assesses vitamin D stores, which influence PTH and calcium absorption.
Creatinine and eGFR: Measure kidney function, which is needed to interpret PTH, phosphorus and vitamin D.
Calcium in 24-hour urine: Quantifies how much calcium is excreted over a full day.
Calcium clearance (calculated): Relates blood and urine calcium to help distinguish between causes of hypercalcaemia.

How to prepare

Fast for 8 to 12 hours. You can drink water. Do not change calcium or vitamin D supplements on your own, and write down the dose you take.

Urine must be collected over 24 hours. Discard the first void, note the time and keep all the following ones, including the first one the next day at the same time. Store the container according to the partner centre's instructions and have the blood sample taken when you hand it in.

You can add

Without another needle. It is offered when you order, so you do not have to decide now.

General blood testA general blood test with full blood count, glucose, cholesterol and kidney and liver function: the basic parameters included in any general check-up.+€59.00
Thyroid functionBrings together TSH and free T4, the two basic tests for assessing how the thyroid is working.+€29.00

Related blood tests

We have other profiles in Other tests with more or fewer tests:

The most comprehensive is not always the most useful. If you are not sure, the one we recommend to start with is High prolactin assessment.

Often checked together with

They are done from the same sample, so there is no extra visit.

Metabolic assessment of kidney stones (blood and 24-hour urine)If the reason for checking calcium is kidney stones, the full kidney stone test adds the 24-hour urine with oxalate, citrate and uric acid, which is what decides the treatment.€179.00

What it is based on

Fifth International Workshop · J Bone Miner Res 37(11):2293-2314
Evaluation and Management of Primary Hyperparathyroidism: Summary Statement and Guidelines from the Fifth International Workshop
Defines primary hyperparathyroidism as raised albumin-corrected calcium together with a high or inappropriately normal intact PTH, confirmed on two occasions at least two weeks apart: that is why this profile measures albumin and not just calcium. The evaluation it then proposes is the one in this protocol: intact PTH, 25-OH vitamin D, phosphorus, creatinine and eGFR. Magnesium is not on that list and is included for the other side of the problem, low calcium, where hypomagnesaemia explains a PTH that does not rise as it should.

Protocol designed by Dr. Antonio Mas, specialist in Endocrinology and Nutrition, Spanish medical licence no. 080846289, and reviewed in September 2026.

This blood test is a standardised protocol and does not replace a medical consultation. If you have symptoms, a known condition or a complex clinical situation, speak to your doctor.