Vitamin D Deficiency: Symptoms, Who Is Low, and the Test
About 1 in 5 US adults (21%) has low vitamin D, below 50 nmol/L (20 ng/mL), and about 1 in 20 (5.5%) is deficient. Most have no symptoms. When deficiency is severe and long-lasting, it causes bone pain and weak thigh and hip muscles. A blood test is the only way to know.
By Erin Rose Updated October 20, 2026 How we score
Who runs low on vitamin D?
Younger adults most often, not older ones. In our analysis of the newest national blood data, 31% of adults 18 to 39 were below 50 nmol/L, against 10% of adults 60 and older.
| Age | Low (below 50 nmol/L) | Deficient (below 30 nmol/L) |
|---|---|---|
| 18 to 39 | 30.6% | 8.6% |
| 40 to 59 | 19.9% | 5.4% |
| 60 and older | 9.6% | 1.7% |
| All adults | 20.8% | 5.5% |
Symptoms of vitamin D deficiency
Most people with low vitamin D feel fine. These are the symptoms with real evidence behind them, and the ones that do not hold up.
| Symptom | What studies show |
|---|---|
| Bone pain and tenderness | Real, when deficiency is severe and lasts a long time. It is called osteomalacia, soft bones in adults (Bhan 2010). |
| Weak thigh and hip muscles | Real. Women with deficiency had thigh strength about a third lower than others (Glerup 2000). |
| Tiredness | Unclear. One small trial in 120 tired young adults tested it; it does not show vitamin D treats tiredness (Nowak 2016). |
| Low mood | Not shown. In 18,353 adults, vitamin D did not prevent depression (Okereke 2020). |
| Aches and chronic pain | Not shown. A review of 10 trials found no clear benefit over placebo (Straube 2015). |
| Hair loss, frequent colds, slow healing | Often listed online, but we found no controlled trial showing they clear up when vitamin D is fixed. |
What raises your risk
- Little sun: your skin makes vitamin D from sunlight, so long winters and indoor days lower it (Holick 2007).
- Darker skin: the same sun makes less vitamin D.
- Extra weight: after the same sun exposure, vitamin D in the blood rose 57% less in people with obesity (Wortsman 2000).
- Gut conditions or weight-loss surgery that block fat absorption, like Crohn’s or celiac disease (NIH).
- Breastfed babies: breast milk has little vitamin D, so babies need 400 IU a day (NIH).
How to find out
A 25(OH)D blood test. Below 30 nmol/L (12 ng/mL) is deficient, and 50 nmol/L (20 ng/mL) or more is enough for most people. See what your result means.
What to take
Want to stay out of the low range: 2,000 IU a day
A steady 2,000 IU a day helps most adults stay out of the low range. NatureWise D3 2000 IU, on NSF/ANSI 173, gives that in one small softgel, under the 4,000 IU limit.
NatureWise Vitamin D3 2000 IU in Olive Oil
$0.04 a day · 2,000 IU · NSF/ANSI 173
A test showed you are low: follow your doctor’s plan
Doctors often use 5,000 IU a day for a set time, then retest. NatureWise D3 5000 IU, one small softgel in olive oil, is on NSF/ANSI 173. It is above the 4,000 IU adult upper limit, so take it only on your doctor’s advice. If you also want K2, Sports Research D3 + K2 has the same 5,000 IU but is not on a testing list we check.
NatureWise Vitamin D3 5000 IU in Olive Oil
$0.04 a day · 5,000 IU · NSF/ANSI 173
Questions people ask
Can you be low on vitamin D without symptoms?
Yes, and it is the usual case. Mild and moderate deficiency causes no symptoms you would notice. Bone pain and muscle weakness show up only when deficiency is severe and lasts a long time (Bhan 2010).
Should I get tested?
Not just to check. The Endocrine Society’s 2024 guideline advises against routine vitamin D testing for healthy adults (Demay 2024). Ask your doctor if you have a risk factor above or the bone and muscle symptoms. The vitamin D blood test.
Sources
- CDC, National Health and Nutrition Examination Survey 2021–2023, serum 25-hydroxyvitamin D (our survey-weighted analysis of US adults).
- NIH Office of Dietary Supplements, “Vitamin D: Fact Sheet for Health Professionals.” ods.od.nih.gov
- Bhan A, et al. “Osteomalacia as a result of vitamin D deficiency.” Endocrinol Metab Clin North Am. 2010. PubMed 20511054
- Glerup H, et al. “Hypovitaminosis D myopathy without biochemical signs of osteomalacic bone involvement.” Calcif Tissue Int. 2000. PubMed 10821877
- Nowak A, et al. “Effect of vitamin D3 on self-perceived fatigue: a double-blind randomized placebo-controlled trial.” Medicine (Baltimore). 2016. PubMed 28033244
- Okereke OI, et al. “Effect of long-term vitamin D3 supplementation vs placebo on risk of depression or clinically relevant depressive symptoms and on change in mood scores: a randomized clinical trial.” JAMA. 2020. PubMed 32749491
- Straube S, et al. “Vitamin D for the treatment of chronic painful conditions in adults.” Cochrane Database Syst Rev. 2015. PubMed 25946084
- Holick MF. “Vitamin D deficiency.” N Engl J Med. 2007. PubMed 17634462
- Wortsman J, et al. “Decreased bioavailability of vitamin D in obesity.” Am J Clin Nutr. 2000. PubMed 10966885
- Demay MB, et al. “Vitamin D for the prevention of disease: an Endocrine Society clinical practice guideline.” J Clin Endocrinol Metab. 2024. PubMed 38828931