What is a normal calcium level?
2.20 to 2.60 mmol/L, for most UK adults. That’s your adjusted calcium. But the raw calcium figure can mislead you, and one other line on your results is the reason.
On this page
What is a normal calcium level?
For most UK adults, a normal adjusted calcium is 2.20 to 2.60 mmol/L. Most NHS labs use this range, known as the Pathology Harmony range.
Ranges may vary between labs, so check the one printed next to your result.
Exactly 2.6 sits on the edge. The range is written as 2.20 to 2.60, but NICE counts 2.6 or more on two tests as high calcium (hypercalcaemia).
- Below 2.2 mmol/LLow. Below 1.9, or with symptoms, is an emergency.
- 2.2 to just under 2.6 mmol/LNormal for most UK adults.
- 2.6 to just under 3 mmol/LHigh if found on two tests. CKS calls it mild.
- 3 mmol/L or aboveCKS: urgent, usually same-day, referral. Above 3.5 is an emergency.
Sources: Pathology Harmony (Schini 2021); NICE CKS; Society for Endocrinology
On 2.7 and feel well? For mild high calcium with no or mild symptoms, CKS advises a repeat test after one week.
Seeing numbers in mg/dL? That’s the US unit. UK labs such as North Bristol report mmol/L, so compare like with like.
Outside the range? Ask your GP whether you need a repeat test.
What does a calcium blood test measure?
It measures the calcium in your blood. Calcium keeps your bones, muscles and nerves working properly.
Some of it rides on a protein in your blood, like passengers on a bus. NICE says calcium stuck to that protein is not active and has no effect.
That other line is your albumin, the protein. Labs adjust your calcium to a standard albumin of 40 g/L, to give a better picture of the calcium at work.
More or fewer buses changes the passenger count. In the same way, your raw calcium can rise or fall with your albumin. The adjusted line allows for this, so read that one, not the raw one.
| Line | What it is | Normal (mmol/L) |
|---|---|---|
| Calcium (total) | All your calcium, including the part on albumin. | Read the adjusted line instead. |
| Adjusted (corrected) calcium | Your calcium, adjusted for albumin. The one doctors use. | 2.20 to 2.60 for adults |
| Albumin | The protein that carries some of your calcium. | Your lab’s range |
| Ionised calcium | A separate test on blood taken in a special syringe and rushed to the lab on ice. | 1.15 to 1.35 at one NHS lab |
Sources: NICE NG132; North Bristol NHS Trust; Oxford University Hospitals; Liverpool University Hospitals
Very low or very high albumin? Even the adjusted figure may be inaccurate. See the albumin blood test and low albumin guides.
Ionised calcium needs blood taken in a special syringe and rushed to the lab on ice. Ranges differ between labs, so use yours.
Why did my GP order it? NICE advises it for thirst, peeing a lot or constipation. It also advises it for thin bones (osteoporosis), a bone broken in a minor fall, or a kidney stone.
GPs may also check it for long-term symptoms with many possible causes, like tiredness or low mood.
Ask your GP which calcium line they used.
Normal calcium levels by age
| Age | Normal adjusted calcium (mmol/L) |
|---|---|
| Up to 4 weeks | 2.00 to 2.70 |
| 4 weeks to 16 years | 2.20 to 2.70 |
| Adults | 2.20 to 2.60 |
Source: North Bristol NHS Trust
For adults, NHS labs such as Oxford use 2.20 to 2.60 at all ages, for men and women.
Some experts think the top should be lower for some adults. A UK study of adults aged 40 to 69 suggested 2.59 for women aged 55 to 69 and 2.57 for women aged 40 to 55.
For men it suggested 2.55. The researchers say the range should be updated, but labs still use 2.60.
Near the top with symptoms? NICE already advises a repeat from 2.5 with signs of overactive parathyroid glands, such as thirst or a kidney stone.
What does high calcium mean?
High calcium often causes few or no symptoms. The most common cause is overactive parathyroid glands, small glands in your neck that help control calcium.
Many people with overactive parathyroid glands have no, or very mild, symptoms. The NHS lists these:
- tiredness
- aches and pains, especially in your joints, hands, arms, feet and legs
- muscle weakness
- feeling and being sick
- loss of appetite
- constipation and tummy pain
- feeling thirsty all the time and peeing more than usual
- low mood and depression
| Cause | Worth knowing |
|---|---|
| Overactive parathyroid glands (primary hyperparathyroidism) | The most common cause. Usually mild, with no symptoms. |
| Cancer | The second most common cause. Often already known when calcium rises. |
| Medicines | Thiazide diuretics (some water tablets) and lithium (a mood medicine). |
| Too much vitamin D, vitamin A or calcium | Taking too much, for example from supplements or large amounts of calcium antacids. |
| Other causes | Kidney disease, conditions that cause swelling in organs such as the lungs (sarcoidosis) or tuberculosis (TB), a lung infection, and long spells unable to move. |
Source: NICE CKS: causes
High on two tests? NICE advises a parathyroid hormone (PTH) test. CKS advises a hormone specialist (endocrinologist) if overactive parathyroid glands are suspected.
Adults shouldn’t take more than 100 micrograms (4,000 IU) of vitamin D a day, unless a doctor advised a different amount. Some medical conditions mean you may not safely take that much, so ask your doctor. See high vitamin D levels.
On lithium or a water tablet? Never stop or change a prescribed medicine without your prescriber. Your GP may reduce or stop one that could be the cause.
What to do after a high calcium result
- Check you’re reading the adjusted (corrected) calcium line.
- Compare it with the range your lab prints next to it.
- Expect a repeat test if it’s 2.6 or more.
- Tell your GP about any vitamin D, vitamin A or calcium supplements, or calcium antacids.
- Don’t change your diet to lower your calcium unless your specialist tells you to.
- Never stop or change a prescribed medicine without your prescriber.
Sources: NICE NG132; NICE CKS; NHS
What does low calcium mean?
Low calcium is below your lab’s range, usually 2.20. Symptoms typically start below about 1.9, but this varies a lot with how fast it falls.
The Society for Endocrinology lists:
- tingling around your mouth or in your fingers and toes
- muscle spasms and cramps, including in the hands and feet
- a twitch in your face when a doctor taps it, or a hand spasm when a blood pressure cuff is pumped up
- a spasm of the voice box that makes breathing hard
- heart rhythm changes
- seizures (fits)
Severe low calcium, below 1.9 or with symptoms, is a medical emergency treated in hospital. Had a low result and now get these symptoms? Call 111 now, or 999 if it’s life-threatening.
In hospital, the most common cause of sudden low calcium with symptoms is thyroid removal. Neck surgery can damage the parathyroid glands nearby.
Other causes include severe vitamin D deficiency, low magnesium and pancreatitis, a swollen pancreas. Low magnesium can come from PPIs, medicines that cut stomach acid. Never stop or change a prescribed medicine without your prescriber.
Ask your GP whether to check your magnesium and vitamin D too.
When to speak to a GP
Many people only find out from a test for something else. Speak to a GP if:
- Your adjusted calcium is 2.6 or more, or 2.5 or more with signs such as thirst or a kidney stone. NICE advises repeating the test.
- You’re thirsty, peeing a lot or constipated, or you have thin bones, a kidney stone or a bone broken in a minor fall. NICE says to check your calcium.
- You get tingling in your fingers, toes or face, or muscle spasms. After neck or head surgery, contact your surgery team first.
- You’ve been told your calcium is 3.0 or more: contact your GP the same day.
Call 999 if someone has a seizure for the first time. Also call if it lasts longer than usual for them, or over 5 minutes if you don’t know. Don’t drive yourself to A&E.
Kidney disease is one cause of high calcium. See kidney function tests and bone health blood results.