What Your Bone Bloods Show, and What Only a DEXA Can

1. Can a blood test diagnose osteoporosis?

No. The Royal Osteoporosis Society says it in one line: blood and bone marker tests are not used to diagnose osteoporosis or to find out your chance of breaking a bone. That job belongs to a DEXA scan, which measures how dense your bones are.

So why do bloods come into it? Because a handful of treatable conditions speed bone loss up, and bloods are how a GP finds them. The same page says blood tests are sometimes used to diagnose and rule out medical conditions that can cause osteoporosis. That is the job they do here. Not a verdict on your bones. A search for the things acting on them.

The scale is worth knowing. The Royal Osteoporosis Society estimates 3.5 million people in the UK have osteoporosis, and counts more than 500,000 fragility fractures a year. Half of women and 20% of men over 50 will break a bone because of it.

And there is nothing to feel on the way there.

“Osteoporosis is not usually painful until a bone is broken.”

— NHS, Osteoporosis

That is the whole problem with bone. There are no symptoms to react to. Which is exactly why the numbers already sitting on a blood report earn a proper read.

2. What does each number say about bone?

Four results on a standard report have something to say. Here is what each one means, in plain words.

Vitamin D: start here

Vitamin D is the number to look at first. The NHS explains why in one sentence: vitamin D helps regulate the amount of calcium and phosphate in the body, and those nutrients are needed to keep bones, teeth and muscles healthy.

Run low for long enough and adult bone softens rather than thins. The NHS calls that osteomalacia, and names it as what a lack of vitamin D can lead to in adults. Softening and thinning are not the same thing, and it matters which one a low reading points at.

Your result is reported as 25-hydroxyvitamin D, the storage form, in nmol/L. NHS prescribing guidelines read it in three bands. Below 25 is deficient. 25 to 50 may be inadequate. Above 50 is sufficient for most people. If yours sits in that awkward middle band, our guide on borderline vitamin D levels covers what to do about it.

Thyroid: TSH, free T4 and free T3

An overactive thyroid strips bone faster. The Royal Osteoporosis Society is direct about it: a high level of thyroid hormone can increase the rate of bone loss.

There is a version of this that catches people out. The same page adds that people can also have high levels of thyroid hormone if they take too much thyroxine to treat an underactive thyroid. So a levothyroxine dose set slightly too high can do what an overactive gland does. That is a conversation about your dose, with the clinician who set it.

Reading the three markers: TSH is the pituitary gland's instruction to your thyroid, so it runs low when there is already too much hormone about. Free T4 and free T3 are the hormones themselves. A low TSH alongside a high free T4 is the pattern that points at overactivity. Our thyroid hub has the full read, and overactive thyroid symptoms covers what else comes with it.

ALP, or alkaline phosphatase

ALP is an enzyme made in two main places: your liver, and the cells that build bone. So a raised ALP is a question rather than an answer. If your liver markers read normal and ALP is up, bone turnover is one of the things a clinician will think about.

It also moves for ordinary reasons. It runs higher in teenagers who are still growing, higher in pregnancy, and higher while a fracture knits back together. Our ALP blood test guide has the ranges, and ALP levels by age shows how much the number shifts across a lifetime.

Albumin and total protein

These two read your protein status, and they earn a place here for two reasons. Bone is roughly a third protein by weight, so months of eating too little shows up in bone as well as muscle.

Albumin also carries much of the calcium in your blood. That is why labs use it to adjust a calcium result. A low albumin makes a calcium number read lower than the calcium actually available, which is a common reason a calcium result confuses people. Our albumin guide and total protein guide go further.

Neither is a bone test. They are context, and context is how the rest of a report gets read sensibly. Our guide to blood test results explained walks through the whole page.

3. Which bone tests still need your GP?

Here is the baseline list in full. South West London NHS guidance on osteoporosis and fragility fracture asks for a full blood count, ESR or CRP, serum calcium, albumin, creatinine, phosphate, alkaline phosphatase and liver transaminases. Then serum 25-hydroxyvitamin D, thyroid function tests and a myeloma screen.

We can measure some of that. We cannot measure the rest, and it is better to say so.

Two of those gaps are worth saying out loud. We do not sell calcium or phosphate, and we do not sell a bone profile. If a clinician wants those, that is a GP request. Same for a full blood count, and same for a DEXA scan, which no blood test stands in for.

No single Helvy panel carries all four bone-relevant markers either. Vitamin D sits in General Energy & Wellness (£149) and Vitamins & Minerals (£159). ALP sits only in Thyroid & Vital Organs (£159). To put vitamin D and ALP on one report, the build-my-test tool walks you through picking your own markers.

4. Who loses bone fastest?

Bone loss is not spread evenly. Women lose it fastest in the years around and after the menopause, as oestrogen falls away. The Royal Osteoporosis Society lists early menopause among the conditions that raise the risk, because bones then have less protection for longer. Our menopause hub covers the markers worth tracking through that window, and early menopause blood tests covers the timing question.

In men the equivalent question is testosterone. The same ROS page lists low testosterone in men, noting that some treatments and conditions lower it and that this can increase the chance of osteoporosis and broken bones. Our testosterone levels by age guide shows where a reading sits.

Two last things move these numbers rather than your bones. Vitamin D falls through a British winter for everybody, because from about October to March the sunlight is too weak for skin to make any. And a healing fracture lifts ALP on its own. When you tested changes what the report means.

Frequently asked questions

Related guides