I am a 41-year-old lady living in Riyadh, Saudi Arabia for almost 8 years. I had neck pain and back pain 2 years ago. Then I found out it was due to vitamin D deficiency. I took vitamin D3 drops 15ml once a week for 3 months. After stopping the medication, I got the same symptoms again. Then I took another course of vitamin D3 for 3 more months. Five months later my symptoms returned. When I checked the vitamin D levels, it was less than 10. For the third time my doctor advised me to take another course of medication. But this time he gave me calcium (600mg) and vitamin D3 (800 IU) combination tablets for 2 months. After using this tablet for 2 months I got the same pain and again my doctor extended the medication for another 2 months. Still I am taking this tablet. But my back pain is still there and if I fail to take this tablet the pain is worse. I am also having pain in my right heel and toes while bending. Please I need your advice.
Vitamin D plays an important role in development and maintaining of healthy bones. It is important for maintaining cardiovascular health and a strong immune system as well. Many people with vitamin D deficiency may not have any symptoms, but their bones become weaker due to decreased mineral contents in those bones. This condition is called “Osteomalacia.” The following symptoms may be seen in people with vitamin D deficiency;
- Bone pain and back pain
- Muscle weakness and cramps
- Difficulty in walking and climbing stairs
Mild vitamin D deficiency is observed throughout the world, whereas severe vitamin D deficiency is prevalent in South Asia and Middle-East. 
People who are at risk of vitamin D deficiency are;
- Age above 65 years – they have reduced capacity to produce vitamin D in the skin.
- People with darker skin have reduced production of vitamin D in the skin.
- Reduced sun exposure due to any cause – staying housebound most of the time, concealing clothing, using sunscreen and sunblock creams.
- Pregnant or breastfeeding women, due to increased physiological demands.
- People who may absorb less vitamin D from the diet due to certain medical conditions or surgery involving the digestive tract.
- Taking medicines that affect vitamin D.
- Obese individuals.
- Infants , 
The main factor for vitamin D production is sunlight. Our skin contains the inactive form of vitamin D. When the sunlight directly strikes the skin, the body converts the inactive form into the active form of vitamin D. The active form of vitamin D is called “Vitamin D3.” About 85-90% of vitamin D is obtained in this way. The remainder is obtained from the diet.
Foods which contain vitamin D are;
- Fatty fish – such as tuna, mackerel, sardine and salmon
- Cod liver oil
- Beef liver
- Egg yolks
- Foods fortified with vitamin D – dairy products, orange juice, soy milk and cereals 
Body’s average requirement of vitamin D is 10 micrograms per day (400 IU/day). If this cannot be fulfilled by adequate sun exposure and diet, then a vitamin D supplement would be required.
The main challenge for adequate sun exposure in the Middle-East is the risk of sunburn injury. This can be avoided by exposing to the sun for a short time but repeatedly. The time required to make sufficient vitamin D is typically short, and less than the amount of time needed for skin to redden and burn. At least arms and face should be exposed and the more skin that is exposed, the greater the chance of making sufficient vitamin D. Regularly going outside for a matter of minutes around the middle of the day without sunscreen should be enough. The ideal time for sun exposure is mid-day, when the sunlight is most intense. This does not mean the other times are not beneficial.
Vitamin D3 level less than 30 ng/ml in the blood is considered deficiency and less than 10 ng/ml is severe deficiency. People with severe deficiency would require a replacement dose of vitamin D3 followed by a maintenance dose. There are several ways to provide this. One of which is taking 50,000 IU of vitamin D3 once weekly for 6 to 8 weeks and then maintenance dose of 800-1000 IU daily. This has to be continued as long as the person does not have access to natural sources of vitamin D. 
According to the details provided in the question, it seems a replacement dose of vitamin D3 has been given in the liquid form, but the maintenance dose has not been continued. The calcium and vitamin D3 combination tablets can be used in the maintenance phase but not in the replacement phase.  However, those living in regions where kidney stones are prevalent (e.g. The Middle-East) should be cautious about taking calcium supplements in the long run. This is due to the risk of excess calcium in the body which can lead to formation of kidney stones.
It is also mentioned in the question that despite restarting maintenance dose of vitamin D3, the back pain has not improved. Additionally, there is heel pain and toe pain. This necessitates doctors to look for other causes for these symptoms. Therefore, it is advisable to consult a physician (Internist / VP) for thorough evaluation. The doctor would require to take a detailed history, examine the patient, perform other blood tests and possibly order x-rays.
- Marc K Drezner, Clifford J Rosen, and Jean E Mulder. 2019. Patient education: Vitamin D deficiency (Beyond the Basics). August. Accessed September 28, 2019. https://www.uptodate.com/contents/vitamin-d-deficiency-beyond-the-basics.
- Public Health England. 2016. “SACN vitamin D and health report.” GOV.UK. July 21. Accessed September 28, 2019. https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/537616/SACN_Vitamin_D_and_Health_report.pdf.
- Royal Osteoporosis Society. 2018. Vitamin D and Bone Health in Adults: A Practical Clinical Guideline for Patient Management. Accessed September 28, 2019. https://theros.org.uk/healthcare-professionals/tools-and-resources/clinical-guidance/.