Vitamin D Deficiency Symptoms: Signs, Causes, Levels and Testing
Medically reviewed by Sabeen Munib M.D.Most people with low vitamin D have no symptoms at all, so a blood test is the only way to know your level. When deficiency is more severe or lasts a long time, it can cause bone pain, muscle weakness and aches, and it may add to tiredness. The test to ask about is the 25-hydroxy vitamin D blood test, and treatment is usually a supplement at a dose your doctor sets, since too much vitamin D can also be harmful.
What does vitamin D do?
Vitamin D helps your body absorb calcium from food. That keeps bones strong and helps muscles and nerves work normally. Your skin makes vitamin D when it is in sunlight, and you also get some from foods such as fatty fish, egg yolks and fortified milk, cereal and orange juice.
When vitamin D stays low for a long time, the body cannot absorb enough calcium. In children this can cause rickets, with soft, bowed bones. In adults it can cause osteomalacia, where bones become soft and painful, and it adds to the bone thinning of osteoporosis.
What are the symptoms of vitamin D deficiency?
Mild to moderate low vitamin D usually causes no symptoms. Many people find out only from a blood test. When deficiency is severe or long-lasting, signs may include:
- Bone pain or a deep ache, often in the lower back, hips, legs or ribs
- Muscle weakness, especially in the thighs and hips, such as trouble climbing stairs or getting up from a chair
- Muscle aches or cramps
- Feeling tired or run down
- Bones that break more easily than expected
- In children, slow growth, bowed legs or delayed walking
None of these is specific to vitamin D. Bone pain, weakness and fatigue have many causes, so a blood test is needed before blaming vitamin D.
Wondering about hair shedding? Read our separate post on vitamin D and hair loss
Does low vitamin D cause fatigue?
It can be part of the picture, especially when levels are very low, but tiredness alone is not a reliable sign. Thyroid problems, anemia, poor sleep, sleep apnea, depression and blood sugar problems are common causes too. A good workup for fatigue looks at all of them, not only vitamin D.
Does vitamin D deficiency cause weight gain?
Low vitamin D has not been shown to cause weight gain. The link mostly runs the other way: vitamin D is stored in body fat, so people with obesity tend to have lower blood levels and may need more vitamin D to raise them. Taking vitamin D is not a weight loss treatment.
What causes vitamin D deficiency?
Low vitamin D comes from getting too little, absorbing too little or using it up faster. You are more likely to run low if you:
- Get little sun, for example working indoors, covering most of your skin or always wearing sunscreen
- Have darker skin, which makes less vitamin D from the same amount of sun
- Are an older adult, since aging skin makes less vitamin D
- Have obesity, or have had gastric bypass surgery
- Have a condition that limits fat absorption, such as Crohn's disease, celiac disease, ulcerative colitis or cystic fibrosis
- Have kidney or liver disease, which affects how the body activates vitamin D
- Take certain medicines, such as long-term steroids, some seizure medicines, orlistat or cholestyramine
- Are a breastfed infant who does not get a vitamin D supplement
Even in sunny Southern California, many people spend most daylight hours indoors, so living here does not mean your level is normal.
What is the vitamin D blood test?
The test is called 25-hydroxy vitamin D, sometimes written 25(OH)D. It is a simple blood draw and does not require fasting. It is the standard way to measure how much vitamin D your body has stored. A different test, 1,25-dihydroxy vitamin D, is used only for certain kidney and hormone problems and is not the right test for checking deficiency.
What vitamin D level is normal?
Experts do not fully agree on the cutoffs, and labs may print different reference ranges. In the US, results are usually given in nanograms per milliliter (ng/mL). These are the ranges the NIH Office of Dietary Supplements uses:
- Below 12 ng/mL: deficient, with a risk of rickets in children and soft bones in adults
- 12 to under 20 ng/mL: generally too low for bone and overall health in some people
- 20 ng/mL or higher: enough for bone and overall health in most people
- Above 50 ng/mL: higher than needed, and linked with possible harm at very high levels
Some labs and specialists use 30 ng/mL as the lower limit of normal. That is why two reports can label the same number differently. What matters most is your number in the context of your bones, symptoms and health history.
Should everyone get their vitamin D checked?
No. Routine vitamin D testing is not recommended for healthy adults without symptoms or risk factors. National screening groups have not found enough reason to test everyone, and checking healthy people often leads to treatment that does not change how they feel.
Testing makes more sense if you have:
- Bone pain, muscle weakness, frequent falls or a fracture from a minor injury
- Osteoporosis or low bone density
- A condition that limits fat absorption, or a history of weight loss surgery
- Kidney or liver disease
- A medicine that lowers vitamin D, such as long-term steroids
- An abnormal calcium level on other blood work
How is vitamin D deficiency treated?
Treatment is usually an oral supplement, most often vitamin D3 (cholecalciferol). The dose and how long you take it depend on your level, your age, your weight, how well you absorb fat and any other conditions. Your doctor may recheck your level after a few months.
- The daily amount most adults need from food and supplements is 600 IU up to age 70 and 800 IU after 70
- People who are deficient often need more than that for a period of time, at a dose set by their doctor
- Vitamin D is absorbed better when taken with a meal that has some fat
- Enough calcium from food matters too, since vitamin D and calcium work together for bones
- Sensible sun exposure helps, but sunburn raises skin cancer risk, so sun is not a substitute for testing and treatment
Can you take too much vitamin D?
Yes. For most adults, the upper limit is 4,000 IU a day unless a doctor prescribes more for a set time. Very high doses over weeks or months can raise calcium in the blood. Signs include:
- Nausea, vomiting or poor appetite
- Constipation
- Thirst and frequent urination
- Weakness or confusion
- Kidney stones or kidney damage
Too much vitamin D comes from supplements, not from sun or food. Check the labels of all your supplements, since multivitamins and calcium products often contain vitamin D as well.
When should you see a doctor?
Book a visit if you have ongoing bone pain, muscle weakness, falls or a fracture from a small injury, or if you have one of the risk factors above and have never been tested. Also check in before taking high-dose vitamin D on your own.
Get care soon if you take vitamin D supplements and develop vomiting, severe thirst, confusion or side or back pain that could be a kidney stone.
How Dr. Munib approaches vitamin D deficiency
Dr. Munib starts with your symptoms and history: bone health, falls, digestion, weight loss surgery, kidney or liver problems, medicines and the supplements you already take. If testing makes sense for you, she may order a 25-hydroxy vitamin D level along with calcium and other labs that fit your situation.
If your level is low, the plan depends on how low it is and why. Most often that means an oral supplement at a dose she sets, a recheck later and a look at the cause. If symptoms such as fatigue point to something else, she will look at those causes too.
Read about preventive care and checkups at The Pur Health
The Pur Health also lists a vitamin D shot among its separate wellness services
If you think your vitamin D may be low, or you want to know whether testing makes sense for you, a visit is the place to start. The Pur Health is in-network with most PPO plans, and cash visits are $190 for new patients and $150 for returning patients. Visit our Irvine office at 114 Pacifica, Suite 280, or call (949) 647-5234.