Vitamin D Levels: Normal Range, Deficiency Chart & ng/mL to nmol/L
Vitamin D levels are measured as 25-hydroxyvitamin D, or 25(OH)D. UK guidance calls below 25 nmol/L deficient, says 25–50 nmol/L may be inadequate for some people, and treats above 50 nmol/L as sufficient. US guidance (National Academy of Medicine) links below 12 ng/mL to a risk of deficiency and calls 20 ng/mL or more adequate for nearly everyone. Above 50 ng/mL (125 nmol/L) is higher than needed.
Units: US labs report ng/mL, UK labs nmol/L. ng/mL × 2.496 = nmol/L, so 20 ng/mL is about 50 nmol/L. Report says 30–100 ng/mL? See where that range comes from.
- Deficient
- Possibly inadequate
- Sufficient
- Higher than needed
- Toxic range
- ng/mL to nmol/L
- Is 30 ng/mL the target?
- Pregnancy, children, older age
Where does my vitamin D sit?
Type the number from your report, pick its unit and choose UK or US cut-offs. Everything is worked out on your device, and nothing is saved or sent anywhere.
Result in a different unit? Our blood test unit converter switches vitamin D between ng/mL and nmol/L.
Vitamin D levels chart
The chart uses a log scale. Top numbers are nmol/L, bottom numbers the same points in ng/mL. The rows show where guidelines and labs draw their lines.
Sources: NICE CKS; ROS 2018; NAM (IOM) 2011 via NIH ODS; UHNM pathology; Quest; Labcorp test 081950. Full references below.
| Band | UK (NICE CKS, SACN, ROS) | US (NAM) | What it usually means |
|---|---|---|---|
| Deficient | Below 25 nmol/L (10 ng/mL) | Below 12 ng/mL (30 nmol/L) | Can lead to rickets in children and osteomalacia (soft bones) in adults |
| Possibly inadequate | 25–50 nmol/L (10–20 ng/mL) | 12 to under 20 ng/mL | Enough for some people, not all |
| Sufficient | Above 50 nmol/L (20 ng/mL) | 20–50 ng/mL (50–125 nmol/L) | Enough for bone health in almost everyone |
| Higher than needed | No UK cut-off | Above 50 ng/mL (125 nmol/L) | Linked to potential adverse effects |
| Potentially toxic range | No UK cut-off | Above 150 ng/mL (375 nmol/L) | Where toxicity is typically seen, often with high calcium |
UK cut-offs are set in nmol/L and US cut-offs in ng/mL. Brackets give rounded equivalents. The top two markers come from US sources (NAM; NIH ODS), because UK guidance doesn’t set its own.
What a vitamin D test actually tells you
Think of 25(OH)D as the stock count in your vitamin D warehouse. It shows what has arrived over recent weeks, from every supplier.
Vitamin D comes from sunlight, food and supplements. Your liver turns it into 25-hydroxyvitamin D, which has a half-life of about 15 days, so it reflects your recent supply from all sources (NIH ODS).
Your kidneys make a little of the active hormone, 1,25-dihydroxyvitamin D, which helps you absorb calcium. Its level is tightly controlled and often stays normal until deficiency is severe, so it’s a poor test of your stores (NIH ODS). When vitamin D runs short, you absorb less calcium and the parathyroid glands make more PTH to hold blood calcium steady.
Do you need a vitamin D test at all?
Often not. UK guidance (ROS 2018) says routine testing isn’t needed. Testing makes sense for symptoms of soft bones (osteomalacia), such as bone pain with muscle weakness, known bone disease, or before certain strong bone medicines. The Endocrine Society (2024) suggests against routine testing in every group it studied, including healthy adults, pregnancy, obesity and darker skin.
What your vitamin D number means
Each band is set out like a case file: clues, usual suspects, the next lead your doctor may follow, and questions to ask.
Below 25 nmol/L (UK) or below 12 ng/mL (US)
Both UK and US guidance treat this as deficient. Over time, a level this low can soften the bones, causing rickets in children and osteomalacia in adults (NIH ODS). It’s common and treatable.
- Often no symptoms
- Sometimes bone pain, muscle weakness, or trouble climbing stairs (NHS)
- Little sun on your skin
- Darker skin
- Poor fat absorption or weight-loss surgery
- Some anti-seizure drugs, steroids, orlistat or cholestyramine
A bone profile (calcium, phosphate, alkaline phosphatase) and PTH. After a high-dose course, UK guidance rechecks calcium about a month later (ROS).
UK (ROS, NICE CKS): treat, usually with a high-dose loading course, then a maintenance dose. Your doctor will advise the dose.
Ask: Do I need a bone profile and PTH? What dose, and for how long? Could a gut condition or medicine be involved?
25–50 nmol/L (UK) or 12 to under 20 ng/mL (US)
A gray zone. Enough for some people and not for others, so your wider health decides what happens next.
- Usually no symptoms
- Often a winter test
- Less sun in autumn and winter
- Skipping the 10 micrograms a day the NHS advises everyone to consider in autumn and winter
Your doctor weighs your bones, fracture risk, medicines and symptoms. PTH can help decide.
UK (ROS 2018): treat in this band if you have a fragility fracture, osteoporosis or high fracture risk, take antiresorptive bone medicine, have symptoms or a raised PTH, take anti-seizure drugs or oral steroids, or get little sun. Otherwise, advice on prevention.
Ask: Do I need treatment, or advice on prevention? Do my bones, medicines or PTH change that?
Above 50 nmol/L (UK) or 20 to 50 ng/mL (US)
Enough for bone health in almost everyone. Neither UK nor current US guidance sets a higher target. See the 30 ng/mL question.
- A US report using 30–100 ng/mL flags 20–29 as low, though NAM calls it adequate
- Muscle pain or weakness despite an adequate level points to another cause (Exeter Clinical Laboratory)
Other suspects: low ferritin, vitamin B12, thyroid (TSH), magnesium, sleep and mood. See our “Always tired?” case file.
Ask: Do I still need a supplement? If I still have symptoms, what else should we check?
Above 125 nmol/L (50 ng/mL)
No guideline aims this high. US guidance (NAM) links levels above 125 nmol/L (50 ng/mL) to potential adverse effects, particularly above 150 nmol/L (60 ng/mL). Sunlight can’t cause a vitamin D overdose (NHS), so the usual suspect is supplements.
- High-dose supplements, or several products containing vitamin D
- A prescribed high-dose course
- Frequent tanning bed use (NIH ODS)
NHS: adults no more than 100 micrograms (4,000 IU) a day, children aged 1–10 no more than 50 micrograms (2,000 IU), babies under 12 months no more than 25 micrograms (1,000 IU). The US adult upper limit is also 4,000 IU (NAM).
Ask: Should I lower or stop my supplement? Should we check my calcium?
Above 375 nmol/L (150 ng/mL)
Vitamin D toxicity is typically seen above 375 nmol/L (150 ng/mL), with high blood calcium (hypercalcemia; UK spelling hypercalcaemia) and high urine calcium (NIH ODS). See a doctor the same day.
- High calcium on a blood test
- Possibly nausea, vomiting, muscle weakness, confusion, thirst, passing a lot of urine or kidney stones (NIH ODS)
- Very high-dose supplements over time
- Frequent tanning bed use
Urgent calcium, kidney function and PTH. With high calcium, a low PTH points away from the parathyroid glands (North Bristol NHS Trust).
NIH: toxicity typically comes with total calcium above 11.1 mg/dL (about 2.8 mmol/L). ROS: high calcium should lead to stopping vitamin D supplements.
Ask: Is my calcium high? Should I stop all vitamin D and calcium supplements now?
Vitamin D with calcium and PTH: the patterns
Calcium and parathyroid hormone (PTH) show how your body is coping.
| 25(OH)D | Calcium | PTH | Usual pattern |
|---|---|---|---|
| Low | Normal or low | High | Secondary hyperparathyroidism: PTH rises to hold calcium steady |
| Low | Low or normal, low phosphate, high ALP | Often high | Osteomalacia. Over 80% of adults with it have a high ALP. Low magnesium can show up too. |
| Low or normal | High | Not suppressed | Possible primary hyperparathyroidism. Low vitamin D is ruled out first. Needs a doctor’s review. |
| Above 375 nmol/L (150 ng/mL) | High | Low | Vitamin D excess. Needs a same-day review. |
| Normal | Normal | Normal | No vitamin D or calcium problem on these tests |
Sources: Patient.info Professional; North Bristol NHS Trust; NIH ODS.
What can throw off a vitamin D result
Rule out a planted clue first:
- Season. Levels are lowest in winter and highest in summer (SACN 2016). In the UK, most people make all the vitamin D they need from sunlight from about late March or early April to the end of September (NHS).
- A recent supplement change. Allow at least 3 months of treatment before rechecking, and 6 months may be wiser (ROS 2018). Some NHS labs won’t repeat the test within 6 months (UHNM, North Bristol).
- Different labs. Results can vary by 15–20% between assays (SACN 2016), which the NIH’s Vitamin D Standardization Program (2010) aims to fix. Track trends at the same lab.
- Vitamin D2. Some immunoassays don’t pick up all D2 (ergocalciferol), so the total can read low (ROS 2018). LC-MS/MS measures D2 and D3 separately (Mayo Clinic Laboratories). One NHS area advises against testing people who take D2 (BLMK 2025).
- Acute illness or surgery. Average 25(OH)D fell from 56 to 46 nmol/L 48 hours after hip or knee replacement, as CRP rose. The authors called it an unreliable marker after acute inflammation (Waldron 2013).
- A unit mix-up. 30 ng/mL and 30 nmol/L are very different. Check the unit, or use our blood test unit converter.
Who is more likely to run low
- Little sun on your skin: frail, housebound, in a care home, or covering most of your skin outdoors. The NHS advises considering 10 micrograms (400 IU) a day all year.
- Darker skin, such as an African, African-Caribbean or South Asian background: the same NHS all-year advice. The Endocrine Society (2024) suggests against routine screening on skin color alone.
- Age 65 and over (South East London ICS 2025).
- Obesity (BMI 30 or more), because body fat holds on to vitamin D (NIH ODS).
- Poor fat absorption or weight-loss surgery (NIH ODS), and severe liver disease or end-stage kidney disease (SEL ICS).
- Some medicines: carbamazepine, phenytoin, barbiturates, corticosteroids, cholestyramine (colestyramine in the UK) and orlistat (SEL ICS; NIH ODS).
Pregnancy and breastfeeding
The NHS advises everyone, including pregnant and breastfeeding women, to consider 10 micrograms (400 IU) a day in autumn and winter, and all year in a risk group. The Endocrine Society (2024) suggests vitamin D in pregnancy but suggests against routine testing. Your midwife or doctor will advise.
Babies and children
The NHS advises 8.5–10 micrograms a day for breastfed babies from birth to 1 year, and for babies having less than 500 ml of formula a day. Children aged 1–4 should have 10 micrograms a day all year. The Endocrine Society (2024) suggests supplements for ages 1–18. See a GP if you think your child might have rickets, such as bowed legs or swollen, painful wrists (NHS).
Older adults
The US recommended intake rises from 600 IU to 800 IU a day after age 70 (NAM). The Endocrine Society (2024) suggests supplements from age 75, for a possible lower risk of death, without routine testing.
Is 30 ng/mL (75 nmol/L) the optimal vitamin D level?
The idea that under 30 ng/mL is insufficient comes from one guideline, since replaced.
- Endocrine Society 2011: deficiency below 20 ng/mL, insufficiency 21–29, a target above 30 ng/mL (75 nmol/L), and 30–100 ng/mL as sufficient. Quest, and Labcorp until recently, printed 30–100 ng/mL to match.
- Endocrine Society 2024: replaces the 2011 guideline. It no longer endorses the 30 ng/mL target or any level defining sufficiency, insufficiency or deficiency, and suggests against routine testing.
- NAM 2011: 20 ng/mL (50 nmol/L) is adequate for nearly everyone.
- UK (SACN 2016, ROS, NICE CKS): above 50 nmol/L is sufficient. SACN says no one should fall below 25 nmol/L at any time of year.
Labs differ. Labcorp’s directory now lists 20.0–100.0 ng/mL (updated September 2026). Mayo Clinic Laboratories calls 20–50 ng/mL optimum. Bottom line: 25 ng/mL (62 nmol/L) is adequate by US (NAM) and UK cut-offs, even if your report flags it.
Reading vitamin D on your lab report or app
- Names: 25-hydroxyvitamin D, 25(OH)D, 25-OH vitamin D or 25-hydroxycholecalciferol. If D2 and D3 are listed separately, use the total.
- Units: ng/mL (US) or nmol/L (UK). µg/L is the same number as ng/mL.
- Flags: “H” or “L” only means outside that lab’s range.
- Apps and portals: US portals often show results before your clinician comments. In the UK, the NHS App may add a note from your GP practice.
Vitamin D ng/mL to nmol/L
Multiply ng/mL by 2.496 to get nmol/L, or divide nmol/L by 2.496 (Mayo Clinic Laboratories). Many sources round to 2.5 (NIH ODS).
| ng/mL | nmol/L | Where it sits |
|---|---|---|
| 10 | 25 | UK deficiency cut-off |
| 12 | 30 | US (NAM) deficiency-risk cut-off |
| 20 | 50 | US (NAM) adequacy cut-off; UK sufficient above 50 |
| 30 | 75 | Old Endocrine Society 2011 target |
| 50 | 125 | Above this is higher than needed |
| 100 | 250 | Top of Labcorp and Quest ranges |
| 150 | 374 | Toxicity typically above this |
When to get help urgently
- A vitamin D above 375 nmol/L (150 ng/mL), or a high calcium result: contact your doctor the same day and ask whether to stop your supplements.
- Vomiting, extreme thirst, passing a lot of urine, confusion or severe weakness, especially on high-dose vitamin D: get urgent help (NHS 111 in the UK, urgent care in the US). Go to A&E or the emergency room if you’re severely unwell.
Vitamin D questions people ask
What is a normal vitamin D level?
For most people, 20 ng/mL (50 nmol/L) or more is enough. UK guidance calls above 50 nmol/L sufficient, and US guidance calls 20–50 ng/mL adequate. Above 50 ng/mL (125 nmol/L) is higher than needed.
What vitamin D level counts as deficient?
In the UK, below 25 nmol/L (10 ng/mL). In the US, below 12 ng/mL (30 nmol/L) carries a risk of deficiency (NAM). Some US reports still use below 20 ng/mL, from the 2011 Endocrine Society guideline.
How do I convert vitamin D from ng/mL to nmol/L?
Multiply by 2.496. To go back, divide by 2.496. So 30 ng/mL is about 75 nmol/L, and 50 nmol/L is about 20 ng/mL.
Why does my lab say 30–100 ng/mL is normal?
That range matches the Endocrine Society’s 2011 guideline. Its 2024 guideline no longer endorses the 30 ng/mL target. US guidance (NAM) calls 20 ng/mL (50 nmol/L) adequate, and UK guidance calls above 50 nmol/L sufficient.
Is 20 ng/mL (50 nmol/L) enough?
For nearly everyone, yes, by US (NAM) cut-offs. UK guidance puts exactly 50 nmol/L at the top of its 25–50 band, so your doctor may weigh your bone health and risk factors.
What vitamin D level is too high?
Above 50 ng/mL (125 nmol/L) is higher than needed. Toxicity, with high calcium, is typically seen above 150 ng/mL (375 nmol/L). Supplements can cause it. Sunlight can’t.
How long after starting vitamin D should I retest?
At least 3 months, and UK bone guidance says 6 months may be wiser. Many people never need a retest.
Can low vitamin D make you tired?
Marked deficiency can cause muscle weakness, so walking tires you more easily (NHS). Tiredness has many causes. See our “Always tired?” case file.
How we wrote this page
Written and medically reviewed by Dr. Mustafa Sakr, MBBCh. Last reviewed: October 2026. The numbers come from current guidelines (NICE CKS, SACN, ROS, NAM, Endocrine Society 2024), NIH and published lab ranges, listed below. We update this page when guidance changes.
How the checker works: it compares your 25(OH)D, in the unit you enter, with UK cut-offs of 25 and 50 nmol/L (10 and 20 ng/mL) or US cut-offs of 12 and 20 ng/mL (30 and 50 nmol/L). Both use 125 nmol/L (50 ng/mL) as higher than needed and 375 nmol/L (150 ng/mL) as potentially toxic. Your lab’s range, if entered, sets the low and high limits. Numbers that look like the wrong unit get a hint instead. Nothing is stored or sent, and the checker can’t weigh your symptoms, medicines or history.
References
- NICE CKS. Vitamin D deficiency in adults. Last revised January 2022. cks.nice.org.uk
- Royal Osteoporosis Society. Vitamin D and Bone Health: A Practical Clinical Guideline, 2018 (reviewed 2020). theros.org.uk (PDF)
- SACN. Vitamin D and Health, 2016. gov.uk (PDF)
- Demay MB, et al. Vitamin D for the Prevention of Disease: An Endocrine Society Clinical Practice Guideline. JCEM 2024;109(8):1907–1947. doi:10.1210/clinem/dgae290 · endocrine.org
- Holick MF, et al. Endocrine Society vitamin D deficiency guideline. JCEM 2011;96(7):1911–1930. doi:10.1210/jc.2011-0385
- Institute of Medicine (now NAM). Dietary Reference Intakes for Calcium and Vitamin D, 2011; Ross AC, et al. JCEM 2011;96(1):53–58; CDC Data Brief 59. doi:10.1210/jc.2010-2704 · cdc.gov
- NIH Office of Dietary Supplements. Vitamin D Fact Sheet for Health Professionals; Vitamin D Standardization Program. Fact sheet · VDSP
- NHS. Vitamin D; Rickets and osteomalacia. Vitamin D · Rickets
- Mayo Clinic Laboratories. Test 25HDN; SI unit conversion table. Test · Conversion table
- Labcorp. Vitamin D, 25-Hydroxy, test 081950. labcorp.com
- Quest Diagnostics. Vitamin D, 25-OH, Total sample report, 2022. questdiagnostics.com (PDF)
- NHS labs: UHNM; North Bristol NHS Trust (vitamin D, hypercalcaemia); Exeter Clinical Laboratory. UHNM · North Bristol · Hypercalcaemia (PDF) · Exeter
- NHS South East London ICS, Adult Vitamin D Guideline, 2025; NHS BLMK ICB, Vitamin D Deficiency in Adults, 2025. SEL ICS (PDF) · BLMK ICB (PDF)
- Waldron JL, et al. Vitamin D: a negative acute phase reactant. J Clin Pathol 2013;66(7):620–622. jcp.bmj.com
- Patient.info Professional. Vitamin D deficiency including osteomalacia and rickets, 2025. patient.info
This page is for education only and isn’t medical advice, a diagnosis or a substitute for your own doctor, who knows your history. Reference ranges vary between laboratories. Always interpret results with a qualified clinician. See our medical disclaimer.
