Vitamin D Injection or Tablets: Which Is Right for You?

Every autumn the searches for "vitamin D injection" climb, and every autumn I have the same conversation in clinic. For most people a vitamin D injection is not better than tablets. It is faster to give, it removes the need to remember a daily dose, and for a small group of people it is genuinely the right choice. For everyone else it is a more expensive way of doing what a cheap tablet does just as well. Here is how to tell which group you are in.

Why vitamin D matters

Vitamin D controls how much calcium the gut absorbs, and calcium is what bones and muscles run on. The authorised wording is that vitamin D contributes to the maintenance of normal bones, teeth and muscle function, and to the normal function of the immune system. Severe deficiency causes rickets in children and osteomalacia, a softening of bone with aches and weakness, in adults. Milder deficiency is linked to tiredness, muscle aches, low mood over winter and more frequent infections, although those links are weaker than the internet suggests.

We make most of our vitamin D in the skin from sunlight, and in the UK the sun is too low in the sky from October to March for that to happen at all. Diet provides only a little: oily fish, eggs, fortified cereals and spreads.

How common is low vitamin D?

Very. Around one in five UK adults has a low level by the end of winter. The figure is higher in people with darker skin, because melanin slows vitamin D production, and in anyone who covers up for cultural or medical reasons, works indoors, is over 65, is overweight or has a gut condition that reduces absorption. In Birmingham, with its large South Asian, Black African and Caribbean communities, low vitamin D is one of the commonest abnormal results we see.

What NICE and the NHS recommend

The advice is straightforward and it starts with tablets:

• Everyone in the UK should consider 10 micrograms (400 IU) of vitamin D a day from October to March. People at higher risk should take it all year round. This is cheap and available from any pharmacy or supermarket.
• A confirmed deficiency is treated with a loading course of high-dose capsules, typically around 300,000 IU in total spread over six to eight weeks, followed by a maintenance dose of 800 to 2,000 IU daily.
• Insufficiency, the grey zone, usually just needs the maintenance dose.

An injection is not the NHS first choice for most people and most GP practices do not offer one, because tablets work and cost pennies.

When an injection makes sense

There is a group for whom a single high-dose injection into the muscle is the better option, and it is this group that our appointment is for:

• Poor absorption. Coeliac disease, Crohn's, after gastric bypass or sleeve surgery, pancreatic disease and some bowel conditions mean tablets are only partly taken up. An injection bypasses the gut.
• A very low level that needs loading quickly, where a six to eight week course feels too slow and the GP judges a depot dose is appropriate.
• People who will not complete a course. Being honest about this is sensible. If you know you will stop the capsules after a fortnight, one injection that lasts months may suit you better.
• People who cannot tolerate the capsules, for example nausea on high doses, or who struggle to swallow them.

In every case the decision is made by the doctor at the appointment, based on your result, your history and your medicines. It is not something to order off a menu.

Test first

Whichever route you take, the blood test comes first. A vitamin D blood test costs £50, the result is usually back within a day or two, and it answers three questions at once: whether you are low, how low, and therefore what dose you need and whether a second dose should ever be considered. Without it we are guessing, and with vitamin D guessing upwards is not harmless. If the test shows a true deficiency, your NHS GP can prescribe the loading course free, and we will say so.

What happens at the appointment

The appointment is 15 minutes with Dr Ahmed and the price includes a GP assessment. He reviews your vitamin D result and, if you have them, your calcium and kidney results, asks about symptoms, gut conditions, kidney stones and medicines, and confirms whether a high-dose injection is right for you. If it is, he prescribes and gives it into the muscle of the upper arm or buttock. It takes a few seconds. You can drive and go back to work straight away, and the site may be sore for a day.

If it is not right for you, he will say so and tell you what to do instead, which is usually a course of capsules. You will not be charged for an injection you do not have.

Safety: why we do not repeat high doses blind

Vitamin D is fat-soluble, which means the body stores it rather than passing the excess in urine as it does with B vitamins. Too much raises blood calcium, and high calcium causes nausea, thirst, passing a lot of urine, constipation, confusion and kidney stones. It takes a great deal of vitamin D to get there, far more than one loading dose, but the risk is real in people who stack high doses from several sources without checking.

So a second high-dose injection is never given without a repeat blood test showing you still need it. And some people should not have a high dose at all without specialist advice:

• Anyone with high blood calcium, now or in the past.
• Sarcoidosis and some other granulomatous conditions, which make the body over-activate vitamin D.
• A history of kidney stones.
• Kidney disease, where calcium and phosphate are already finely balanced.
• Pregnancy, unless a doctor has specifically advised it. Standard daily vitamin D in pregnancy is recommended; high-dose loading is a different matter.
• A previous allergic reaction to a vitamin D injection or its ingredients.

Breathing difficulty or swelling of the face or lips after any injection is an emergency: call 999.

How long does it last?

A single loading injection raises the level over two to four weeks and the effect lasts for several months, which is why it is a once-a-season treatment rather than a monthly one. It does not replace an ongoing maintenance dose. After loading, whether by injection or capsules, most people need 800 to 2,000 IU a day through winter to stay in range, and that is a tablet from the chemist, not another appointment. We recheck the level after about three months if there is any doubt.

Where we are

OneMedicine is a CQC-registered clinic at 1 High Street, Kings Heath, Birmingham B14 7AR, opposite Kings Heath railway station, with free parking at the rear of the clinic. Appointments are booked online and you do not need a referral.

Frequently asked questions

How much does a vitamin D injection cost?

Our appointment is £65 and includes the GP assessment. The vitamin D blood test to find out whether you need one is £50. If your result shows a true deficiency, the NHS can prescribe a loading course of capsules free of charge.

Is a vitamin D injection better than tablets?

Not for most people. A proper course of high-dose capsules raises the level just as well. The injection wins when you cannot absorb tablets, will not finish a course, or need a depot dose quickly under GP assessment.

Can I get a vitamin D injection on the NHS?

Rarely. The NHS treats deficiency with capsules, and most practices do not stock the injection. It is reserved for people with malabsorption or other specific reasons, usually through a specialist.

How often can I have a vitamin D injection?

Once a season at most, and a repeat high dose is only given after a blood test shows you still need it. Between injections you take a maintenance tablet. Repeated high doses without testing risk raising your calcium.

What are the benefits of a vitamin D injection?

In someone who is deficient, restoring vitamin D supports normal bones, teeth, muscle function and the immune system. The benefit comes from correcting the shortfall, not from the needle. In someone with a normal level there is no benefit to add.

What are the side effects?

A sore injection site for a day is the usual one. The important risk is from too much vitamin D over time, which raises calcium and can cause nausea, thirst and kidney stones, which is why we test before any repeat dose. Allergic reactions are very rare.

Can I get a vitamin D injection at Boots or a pharmacy?

Some high-street providers offer vitamin D injections, usually without a blood test. Our view is that the test should come first, so that the dose matches the result and nobody is given a high dose they do not need.

Is there a vitamin D injection near me in Birmingham?

Yes. We give them at our clinic in Kings Heath, opposite the railway station, with a GP assessment included in the appointment. Book online and bring your blood result if you already have one.

Written by Dr Ibrar Ahmed — MBChB MRCP MRCGP PhD PG Dip (Cardiology)
Specialist interest: Cardiovascular Medicine · OneMedicine, CQC-registered clinic