Osteomalacia is a condition affecting adults where the bones become weak and softer than normal. Symptoms include aches, bone pain and muscle weakness. The condition is usually caused by lack of vitamin D, and can be treated by taking extra vitamin D. It can be prevented by ensuring a good supply of vitamin D through sunshine on the skin and/or vitamin supplements. People more likely to get osteomalacia are: pregnant and breastfeeding women, the elderly, people who have dark skin or who don't get much sun on their skin, and those with certain medical conditions. These people should take vitamin D supplements to prevent osteomalacia.
What is osteomalacia?
Osteomalacia is a condition affecting bones and muscles. Normally, bones get their strength from a mineral containing calcium and phosphate. In osteomalacia, there is not enough mineral in the bones, so they are too soft and are prone to pain and fractures. Osteomalacia only affects adults. In children, whose bones are growing, the same condition is called rickets. (There is a separate leaflet on rickets.)
Osteomalacia is not the same as osteoporosis. In osteoporosis, the bones are "thinner", meaning there is less bone, but the amount of mineral in the bones is normal. (See separate leaflet on 'Osteoporosis'.)
What causes osteomalacia?
The usual cause is lack of vitamin D. It is vitamin D which regulates the bone building process and the way the body handles calcium and phosphate. Lack of vitamin D is actually very common, but when it is severe or prolonged then osteomalacia can result. The lack of vitamin D also leads to muscle weakness which is part of osteomalacia.
Vitamin D comes mainly from sunshine and partly from food. Most vitamin D is made by the body itself when sun shines onto the skin. People can lack vitamin D if they spend too much time indoors, or cover up when outside. The problem is worse in cold climates, and for people with dark skin, because the effect of the sun on the skin is less. Some vitamin D is obtained from certain foods: liver, oily fish (such as herring, sardines, pilchards, salmon, tuna and mackerel) and egg yolk. A diet low in these foods will also contribute to a lack of vitamin D - but the main cause of the problem is lack of sunlight on the skin.
Osteomalacia can also be caused by certain medical conditions which affect the way the body processes vitamin D or calcium. Some examples are:
Problems affecting the absorption of food and vitamins from the gut, such as in coeliac disease and Crohn's disease.
Some types of liver or kidney disease (because the liver and kidneys are involved in processing vitamin D).
Drugs which affect vitamin D: carbamazepine, phenytoin, primidone and barbiturates.
Some rare conditions which affect bone mineralization. This includes some rare inherited conditions and aluminium poisoning.
How common is osteomalacia?
We don't know exactly how common it is. Possibly, it is under-diagnosed, or not recognised enough in people who have symptoms such as bone pain. We know that vitamin D deficiency (which can lead to osteomalacia) is very common in the UK - it affects about 1 in 7 adults overall, and as many as 9 in 10 South Asian adults.
Who gets osteomalacia?
Mostly, people get osteomalacia because they have a severe lack of vitamin D, and the groups of people most at risk of this problem are:
Pregnant or breastfeeding women (because much of their vitamin D goes to the baby).
People who get very little sunlight on their skin such as those who stay indoors a lot, or cover up when outside, for example, if wearing a veil.
People with dark skins (because less sunshine gets through the skin) or people of South Asian origin.
People with a family history of vitamin D deficiency.
People having a vegetarian or vegan diet.
People over 65 years old.
People with conditions that affect the way the body handles vitamin D such as those with coeliac disease, Crohn’s disease, and some types of liver and kidney disease.
People taking certain medicines: carbamazepine, phenytoin, primidone or barbiturates.
What are the symptoms of osteomalacia?
Sometimes the symptoms of osteomalacia are very vague, with a general sense of not being well, and aches or pains. A common symptom is bone pain which comes on gradually and stays. This pain is often in the low back and hips, but in severe cases all the bones may be aching and painful.
Other symptoms are:
Bone tenderness - bones feel painful to moderate pressure (often more noticeable in the ribs or shin bones).
Muscle weakness, often noticed as difficulty climbing stairs or when getting up from the floor or a low chair. Sometimes, people who have osteomalacia walk in a "waddling" pattern because of the muscle weakness.
How is osteomalacia diagnosed?
It may be suspected from your medical history, symptoms, or lifestyle. Blood tests are helpful for diagnosis. Blood can be tested for vitamin D, which will show whether vitamin D levels are low. Also, blood tests that detect problems with the liver or bone may show changes linked to osteomalacia. Sometimes osteomalacia shows up on an x-ray, but x-rays are not usually necessary.
Usually, the symptoms plus blood tests are enough to make the diagnosis. Extra tests may be needed if the cause of the osteomalacia is in doubt, or if there are other vitamin or mineral deficiencies. For example, if anaemia is found as well, you should have a blood test to look for coeliac disease. More tests may be needed if you have another medical condition which is contributing to the problem.
How is osteomalacia treated?
Note: if you are pregnant or breastfeeding, see the next section after this.
The usual treatment is to take vitamin D supplements. Rarely, if osteomalacia is not caused only by vitamin D deficiency, other treatments may be needed. Vitamin D is usually taken as a medicine called ergocalciferol or calciferol. The dose of ergocalciferol is written in units known as international units or IU. Some people use micrograms (μg) instead, which are not the same as units. There are various different ways of taking vitamin D, which are:
A single small injection of vitamin D will last for about six months. This is a very effective and convenient treatment. It is useful for people who do not like taking medicines by mouth, or who are likely to forget to take their tablets.
High dose tablets or liquids
There are different strengths available and a dose may be taken either daily, weekly or monthly. This will depend on your situation and on which particular treatment guideline your doctor is using. Always check with your doctor that you understand the instructions - with high doses of vitamin D it is important to take the medicine correctly. The advantage of the higher dose treatment is that the deficiency improves quickly - useful if you have troublesome symptoms.
Standard dose tablets, powders or liquids
These need to be taken every day for about 12 months in order that the body can "catch up" on the missing vitamin D. This is a rather slow method of replacing vitamin D, but is suitable for prevention, or when higher doses cannot be used. A disadvantage of these medicines is that they contain either calcium or other vitamins, giving them a strong taste which some people dislike.
Note, care is needed with vitamin D supplements in certain situations:
If you are taking certain other medicines: digoxin or thiazide diuretics such as bendroflumethiazide. In this situation, avoid high doses of vitamin D, and digoxin will need monitoring.
If you have other medical conditions: kidney stones, some types of kidney disease, liver disease or hormone disease. Specialist advice may be needed.
Vitamin D should not be taken by people who have high calcium levels or certain types of cancer.
You may need more than the usual dose if taking certain medicines which interfere with vitamin D. These are: carbamazepine, phenytoin, primidone and barbiturates.
If you are pregnant or breastfeeding
It is especially important to take treatment for osteomalacia if you are pregnant or breastfeeding. This is both for the mother's and the baby's health. While the baby is inside the womb, its vitamin D comes from the mother. So, if a woman has osteomalacia, treatment is essential to prevent the baby having low vitamin D, which could affect its growth and development.
The treatment for osteomalacia for pregnant and breastfeeding women is also to take vitamin D. However, the doses used are lower than for women not pregnant or breastfeeding, to ensure that the baby does not get too much vitamin D in the womb or in the breast milk. At present, doctors are not sure what is the best dose of vitamin D in this situation. Doses of 1000 units daily (25 micrograms daily) are often used. This is a safe dose for the baby, but may be a rather low dose for the mother. Some research suggests that higher doses can be used, but we are waiting for more guidance on this subject.
Important note: if you are pregnant, do not take supplements containing large amounts of vitamin A. Supplements labelled as suitable for pregnancy are safe to use. Also, do not eat liver which contains large amounts of vitamin A, as too much can harm the baby. Vitamin A can be taken if you are breastfeeding.
If you are breastfeeding and have osteomalacia with low vitamin D, your baby will need vitamin drops. Your milk will not have enough vitamin D for a growing baby (unless you are being treated with very high doses of vitamin D, which is not usually recommended). So, it is a good idea to discuss vitamin drops for the baby with your doctor or health visitor. Free vitamin drops are available with the Surestart scheme.
Are there any side-effects from treatment?
It is very unusual to get side-effects from vitamin D or calcium supplements if taken in the correct dose.
Doses of vitamin D or calcium which are too high can raise calcium levels in the blood. This would cause symptoms such as thirst, passing a lot of urine, reduced appetite, nausea or vomiting, dizziness, and headaches. If you have these symptoms, see a doctor immediately so that your calcium level can be checked by a blood test.
Some guidelines advise that people taking high vitamin D doses should have their calcium levels checked regularly during the first few weeks of treatment. In practice, this is not usually done unless there are symptoms of high calcium as described above.
Are there any complications of osteomalacia?
Osteomalacia causes weakening of the bones, which is improved by treatment. However, until treated, the bones are more prone to fractures (breaks). Severe osteomalacia can cause small fractures in more than one place at a time - for example, in the pelvis, thigh or ribs. Prolonged osteomalacia, if treated very late, can cause bone deformities such as kyphosis (bending of the spine) or curving of the long bones in the arms and legs.
Osteomalacia sometimes causes low levels of calcium in the blood. Theoretically, low calcium can lead to muscle spasms (cramps) or seizures - but in practice this is unlikely to happen.
What is the outlook for osteomalacia?
If treated, the outlook is very good. Most cases of osteomalacia recover with vitamin D treatment. However, it can take time (weeks or months) for bones to recover. So, if you have symptoms such as bone pain, this will also take time to improve.
With prolonged or untreated osteomalacia, the risk of getting osteoporosis (bone thinning and fractures in old age) may be increased. It is also possible that the risk of getting other diseases might be increased. This is because vitamin D is thought to help prevent some conditions such as diabetes, heart disease and cancer.
How can osteomalacia be prevented?
Vitamin D supplements are recommended for adults who are likely to be lacking in vitamin D (see 'Who gets osteomalacia?' above). However, people at very high risk, such as those who get no sunshine, and the elderly, probably need more - approximately 800 units (20 micrograms) daily.
Pregnant and breastfeeding women
If you are pregnant or breastfeeding you should take vitamin D supplements, both for your own health and to help prevent rickets in your baby. 400 units (10 micrograms) daily of vitamin D is recommended for all pregnant and breastfeeding women. Some experts think that women who get very little sunshine need a higher preventative dose such as 800 units (20 micrograms) daily. Pregnant women can get free prescriptions and vitamins.
Suitable supplements for pregnancy are either a calcium/vitamin D tablet, or a multivitamin tablet labelled as suitable for use in pregnancy. Do not take supplements containing large amounts of vitamin A (see the note about this in the 'If you are pregnant or breastfeeding' section above).
Lifestyle changes to prevent osteomalacia
Vitamin D deficiency and osteomalacia can also be prevented by lifestyle changes (to get more sunshine and improve the diet). However, many people find it hard to change their lifestyle, in which case supplements are advised.
Foods containing good amounts of vitamin D are: liver, some fish (mainly oily fish such as herring, sardines, pilchards, trout, salmon, tuna and mackerel), egg yolk, and 'fortified' foods (which have vitamin D added) such as some margarines and breakfast cereals. Do not eat liver if you are pregnant (see the note about this in the 'If you are pregnant or breastfeeding' section above.)
Sunshine: 15 minutes daily from April to September, with hands, arms and face uncovered, is said to be enough for fair-skinned people. Direct sun on the skin is needed, not through glass, clothes or sunscreen. Darker-skinned people will need more sunshine (we don't know how much more). However, in winter in cold climates, there is not enough sunshine to maintain vitamin D levels.
Some special circumstances
People with certain medical conditions which make them prone to osteomalacia and vitamin D deficiency - will need extra vitamin D. The dose needed will depend on which medical condition it is. See 'What causes osteomalacia?' above for a list of these conditions, and discuss vitamin D with your doctor.
If you have been treated for osteomalacia
After osteomalacia has been treated, prevention will be needed so that it does not recur in the future. Most people diagnosed with osteomalacia will need to take vitamin D supplements long term. These can be either vitamin drops/tablets taken daily, or stronger vitamin D medicines/injections taken at longer intervals such as monthly or six-monthly. It would be sensible to discuss prevention with your doctor.
The Arthritis Research Campaign
Copeman House, St Mary's Court, St Mary's Gate, Chesterfield, Derbyshire, S41 7TD
Tel: 01246 558033 Web: www.arc.org.uk
Publishes leaflets about osteomalacia in Urdu, Punjabi, Hindi, Gujarati and Bengali.
Drug and Therapeutics Bulletin, April 2006 44: 25-29. Primary vitamin D deficiency in adults. (Requires a subscription)
Holick MF; Vitamin D deficiency. N Engl J Med. 2007 Jul 19;357(3):266-81.
Dobson, R; Many young south Asian women in UK lack vitamin D: reporting recent research. British Medical Journal 2007;334:389 (24 February)
Wheeless' Textbook of Orthopaedics; Osteomalacia
Scientific Advisory Committe on Nutrition; Update on Vitamin D, February 2007.