5 Signs You Might Be Low on Vitamin D — and Why Most People Have None
THE SHORT ANSWER
Most people who are low on vitamin D have no symptoms whatsoever. That is the single most important thing on this page, and it is why every other "signs" article about vitamin D is slightly dishonest. When symptoms do appear they are usually mild deficiency showing up as fatigue and aching, or severe deficiency showing up as bone pain and weakness in the hips and shoulders. There is one physical test you can do in ten seconds, described below. But the only thing that actually answers the question is a blood test.*
01Why this article argues against itself
Vitamin D deficiency is frequently described as silent, and clinicians make the point that many people are deficient without knowing, partly because levels are not routinely checked.
So a list of signs has a built-in problem. If you have none of them, that tells you very little. Absence of symptoms is not evidence of sufficiency.
That is a strange thing for us to open with, given we sell vitamin D. It also happens to be the truth, and it leads somewhere useful: this is the one nutrient where testing genuinely changes the answer.
021. Bone pain when you press your breastbone or shin
This is the closest thing to a distinctive physical sign, and almost nobody mentions it.
Clinical descriptions of vitamin D deficiency include throbbing bone pain that can be brought on by firm pressure over the sternum or the tibia — the front of the shin.1 The mechanism is osteomalacia: without adequate vitamin D, calcium is not properly incorporated and existing bone mineralises poorly, leaving it softer and tender.
Press firmly on your breastbone with a thumb. Do the same on the flat front of your shin. Sharp local tenderness in both, unrelated to any injury, is worth mentioning to a doctor.
It is not proof. Plenty of things cause bone tenderness. But it is far more specific than tiredness.
032. Weakness in the hips and shoulders specifically
The pattern that matters is proximal muscle weakness — the large muscles closest to the trunk, rather than grip or forearm strength.1,2
In practice it looks like difficulty rising from a low chair without using your arms, struggling on stairs, or trouble lifting things overhead. In older adults it shows up as unsteadiness and a higher risk of falls.
Notably, muscle weakness can appear in deficiency without any biochemical sign of bone involvement, so it can precede anything showing on a standard bone panel.
043. Symmetrical low back pain
Low back pain that is symmetrical — both sides equally, rather than one-sided or radiating — appears in clinical descriptions of deficiency.1
The asymmetry is the useful detail. One-sided back pain that shoots down a leg is a mechanical or nerve problem. A dull even ache across the lower back, alongside the other items here, fits the deficiency pattern better.
054. Fatigue that does not respond to sleep
We are putting this fourth on purpose. Observational studies report higher fatigue scores in people with low levels, and some small trials report modest improvement after correcting a deficiency.
But fatigue is the least discriminating symptom in medicine. Everything causes it. On its own it means very little; alongside bone tenderness and proximal weakness it becomes part of a picture.
065. Frequent respiratory infections
The best evidence here is a 2017 individual-participant-data meta-analysis published in the BMJ, which found vitamin D supplementation protective against acute respiratory tract infection — with the benefit concentrated in those who were most deficient at baseline.3
Again the same shape as iron, zinc and magnesium: repletion helps the depleted, and does much less for everyone else.
07The numbers, and why doctors argue about them
Deficiency is commonly defined as a 25-hydroxyvitamin D level below 20 ng/mL (50 nmol/L). Between 20 and 30 ng/mL is often labelled insufficient. Above 30 ng/mL is generally considered adequate for bone health.
Severe deficiency — below roughly 12 ng/mL (30 nmol/L) — is where the musculoskeletal consequences become clear-cut: osteomalacia in adults and proximal muscle weakness, both of which reverse with treatment.2,4
Two things worth knowing about the disagreement. Guidelines differ on the target, and reasonable clinicians land in different places. And there is no established benefit above about 50 ng/mL, which is worth remembering before taking very high doses.
The honest summary: at the low end the evidence is strong and the treatment works. In the middle it is genuinely contested.
08Who is actually at risk
Darker skin, because more melanin means less vitamin D synthesised from the same sun exposure. Limited time outdoors. Living at higher latitudes, where winter sun is too weak for skin synthesis regardless of how long you stand in it. Obesity, since vitamin D is fat-soluble and sequesters in adipose tissue. Malabsorption conditions. Older age. Consistent use of sunscreen or full covering.
If several of those apply to you, that matters more than any symptom on this page.
09What we would actually do
Ask for a 25-hydroxyvitamin D test. It is inexpensive and it is the only thing that answers the question. We made the full argument in the question a blood test answers better than a label.
If you are low and supplementing, D3 travels with K2 for reasons covered in why D3 travels with K2, and ours are formulated together. Take it with a meal containing some fat — it is fat-soluble, and a black coffee will not do it. Timing is in the timing guide.
And take magnesium seriously alongside it: magnesium is a required cofactor in the enzymes that convert vitamin D to its active form, so low magnesium can blunt what supplemental D is able to do.
10Frequently asked questions
Can you be vitamin D deficient without symptoms?
Yes, and it is the usual case. Deficiency is frequently silent, which is exactly why testing matters more than symptom-spotting.
What is the fastest way to check?
A 25-hydroxyvitamin D blood test. Below 20 ng/mL, or 50 nmol/L, is commonly used to define deficiency.
What does vitamin D bone pain feel like?
A deep throbbing ache rather than a sharp pain, and it can be provoked by firm pressure over the breastbone or the front of the shin.1
Can low vitamin D cause muscle weakness?
Yes, characteristically in the hips and shoulders rather than the hands, and it can appear before bone markers change.
Is more vitamin D better?
No. There is no established benefit above roughly 50 ng/mL, and it is fat-soluble, so excess accumulates rather than being excreted.
Does sunscreen cause deficiency?
It reduces synthesis, but latitude and season matter more. In winter at higher latitudes the sun is too weak for skin synthesis regardless of what you are or are not wearing.
11References
- Recognition and management of vitamin D deficiency. Am Fam Physician. 2009;80(8):841–846. — symmetric low back pain, proximal muscle weakness, bone pain on sternal or tibial pressure.
- Vitamin D testing and treatment: a narrative review of current evidence. Endocr Connect. 2019;8(2). PMCID: PMC6365669.
- Martineau AR, Jolliffe DA, Hooper RL, et al. Vitamin D supplementation to prevent acute respiratory tract infections: systematic review and meta-analysis of individual participant data. BMJ. 2017;356:i6583.
- Is it reasonable to ignore vitamin D status for musculoskeletal health? PMCID: PMC7886074.
*These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease. This article describes clinical signs for general information and is not a diagnostic tool. Persistent bone pain or muscle weakness deserves a doctor.
