What if you were at higher risk of Covid but didn’t know about it? What if that information was available on standard blood tests done at your GP’s surgery? And what if acting on these tests could quickly reduce your risk of Covid? Wouldn’t you want to know?  I will explain.


            A recent paper by Kaufman analysing results from over 190,000 patients in the USA found the lower your blood Vitamin D level the higher your risk of getting severe Covid. Conversely the higher the level of Vitamin D the more you were protected.

         The risk was particularly high in those with Vitamin D levels below 75nmol/l. These low levels are all too common, if not typical, in the UK in winter. To protect yourself from Covid you need blood levels not only in the normal range for Vitamin D (which is between 75 and 150nmol/l) but ideally in the upper part of that range. What was striking about the study was that those with levels of 125 had almost double the protection as compared to those with levels of 75. Above 125 there was only minimal extra benefit (but see later study below  which suggest higher levels may give further benefit). In other words, you want your blood Vitamin D level to be 125 nmol/l or higher.

     The virus uses the ACE2 receptor to gain entry into the cells of our body. Vitamin D blocks this receptor (if there is enough).

         Research at the University of Copenhagen has found that if Vitamin D is deficient, T cells don’t get activated, the immune system malfunctions and doesn’t mobilize against an invader. 

      Another study by Jain of 154 younger patients (30 to 60 years) seen at hospital with Covid compared those who were asymptomatic with those who had severe disease. The asymptomatic had significantly higher mean Vitamin D levels: 27.89 ng/ml (69 nmol/l) versus 14.35 (35.8) in those with severe disease. Put another way there was Vitamin D deficiency in 98.4% of the severe group and 43.9% of the asymptomatic. The fatality rate of the Vitamin D deficient group was 21% against 3.1% in those without deficiency. Of those with severe Vitamin D deficiency,<10ng/ml (<25nmol/l), 52 were in the critical group and only 10 were asymptomatic. Like Alipio’s study this again demonstrates the massive impact Vitamin D has on the outcome in Covid 19.

     And yet another study from Boston and New York following 144 patients with Covid 19 found those with Vitamin D deficiency had almost treble the mortality  (25.3% against 9.2% in those with normal levels).

     Patients admitted to hospitals in Newcastle have had their Vitamin D levels tested. A staggering 81% of those admitted to ITU had low levels (<50nmol/l). After supplementing with high dose Vitamin D they now have one of the lowest deaths rates from Covid 19 in the UK.  

      A study from the University of Heidelberg looked at risk factors of 185 people diagnosed with Covid-19. It investigated the relationship between risk factors and the chance of patients needing ventilation or dying.  

      Let’s have a look at what they found:-

Sex: Males had a 2.5 X increased risk of ventilation and a 2.5 X  increased risk of death  

Age: Over 60s had a 3.2X increased risk of ventilation and a 7.5X increased risk of death.

Co-morbidities (at least one): had a 2.7X increased risk of ventilation and a 5.3 X increased risk of death.

Vitamin D deficiency: had a 7.6 X increased risk of ventilation and a 14.7 X increased risk of death.

     The greatest danger to life, by some ditance, was Vitamin D deficiency.

        A study at Boston University Medical Center last year investigated 287 testing positive for Covid 19. Those patients over 65 with low Vitamin D had 3 times the risk of death, 4 times the risk of septic shock or sepsis and 5 times the risk of acute respiratory distress syndrome. doi: 10.1016/j.eprac.2021.02.013

        A meta-analysis of 8 studies found a negative correlation between Covid 19 mortality and vitamin D levels with a theoretical mortality of zero for those with a Vitamin D levels of 125mmol/l. COVID-19 Mortality Risk Correlates Inversely with Vitamin D3 Status, and a Mortality Rate Close to Zero Could Theoretically Be Achieved at 50 ng/mL 25(OH)D3: Results of a Systematic Review and Meta-Analysis. Nutrients, 2021,13(10):3596) 

         Research from Bar-llan University in Israel looked at 250 patients with Covid 19 (average age 63). These patients had Vitamin D levels measured before onset of the disease (14 to 730 days before). Those with Vitamin D deficiency (levels below 50mmol/l) had mortality 13 times higher (26%) than those with normal levels (2%). Vitamin D deficiency was also associated with more severe disease.  Vitamin D deficiency  was found in 9% of those with mild disease, 56% of those with moderate disease and 87% of those with severe or critical disease. (Are pre-existing Vitamin D deficiencies linked to COVID-19 severity and mortality? Dr L Thomas).  This is yet more research showing that low Vitamin D levels are linked with greater risk of severe Covid 19 disease.

     Have you noticed how coronavirus admissions and deaths plummeted after the warm spring last year when we were bathed in sunshine and hence Vitamin D. (True, we also had the lockdown but subsequent lockdowns have had far less effect).

        But Covid-19 didn’t go away in the summer. What happened is our immunity (and our Vitamin D levels) went up and the virus didn’t trouble us. This is not unique. Every GP knows that viruses start to disappear each year after the first sustained spell of warm weather following winter.

          In Andalucia, Spain, Vitamin D supplements were given to care home residents. This reduced hospital admissions and deaths by nearly 90% in 6 weeks. Vitamin D was also used for inpatients with Covid-19 (using Calcifediol- see below) and deaths dropped from 60 to 3 daily (from 8/11/20) whereas in other locations deaths continued to rise.

       A similar experiment was done in Edmonton, Canada. In one care home, all residents were given 2000 IU of Vitamin D (in 6% of cases this didn’t raise blood levels enough – to 80 nmol/l  so more was added). There were no cases of coronavirus and no deaths in this care home but deaths in surrounding care homes deaths continued unchanged.

        A study was published in Nature (Open) of patients with Covid 19.  One group were given 6000 IU of Vitamin D daily for 8 to 10 days. Another matched group had none. The aim was to increase blood levels of Vitamin D.  They found a highly significant reduction in all inflammatory markers associated with Vitamin D levels of 80-100 ng /ml (equivalent to 200 -250 nmol/l) . As inflammatory markers are known to reflect the severity of the disease, they concluded that Vitamin D reduces severity in Covid 19. Impact of daily high dose Vitamin D therapy on the inflammatory markers in patients with Covid 19 disease. 

        Let’s hope vaccines will be equally effective (however the vaccine will  protect only against Covid 19 whereas Vitamin D will protect against all infections).

      But how much Vitamin D would you need to take. Research by Kimball found many people needed 6000 IU of Vitamin D to reach levels of 100 nmol/l (and more in the obese). Those in the BAME community will require more as they can have very low Vitamin D levels. My experience is most people need less than this (between 2000 and 4000 IU daily). But having Vitamin D checked is the only way to be sure.

       Please note that in Andalucia they used Calcifediol. Why does this matter? Because it is the active form (so it works immediately). If you take standard Vitamin D3 (colecalciferol) it has to be converted in the liver to the active form and this process is slow. It takes 2 weeks to build up a protective blood level unless you start with a very high dose (the equivalent dose to that used in Andalucia would be equivalent to 100,000 IU of Vitamin D3 (colecalciferol) in the first week then 50,000 IU weekly.

          The obvious conclusion is that we all need to be taking Vitamin D supplements and just as important we need to take enough of it.

         Many GPs now prescribe Vitamin D but, in my experience, they often give too little (sometimes as low as 800 IU daily). This simply isn’t enough to give adequate protection as suggested by this research.

        No adverse effects has ever been shown for doses of up to 10,000 IU daily which is the sort of dose you would get after sunbathing for an hour or two. 

        Vitamin D levels is the test least likely of the three to have been done by your GP but the most important. If you have had recent tests it’s well worth know what they were. If you are having routine tests make sure Vitamin D is included.




          Many people are now on drugs to lower cholesterol but few patients and few doctors realise that cholesterol and LDL (sometimes called bad cholesterol) powerfully protect us against infections and could be vital to our immunity against severe Covid infections. 

          Major studies including a meta-analysis of 19 studies and two 15 year studies of 120,000 and 100,000 people have given us definitive answers. There is an inverse association between cholesterol levels and being admitted to hospital with infections. .

Another study found an inverse association between cholesterol and the risk of dying in people with AIDs. In other words, the higher your cholesterol level the better the protection against infections. We also know that LDL protects against bacterial toxins.

         There are now also a few studies on Covid and cholesterol and, as expected, this shows the same pattern with people with lower cholesterol getting more severe disease (1).

         Statins could affect covid in two ways. They are anti-inflammatory which may have a positive effect and they lower cholesterol which could have a negative effect. For those with pre-existing heart disease it makes sense to use the lowest strength of statin. Several studies (see show that the lowest strengths work just as effectively as the higher strengths and with the bonus of fewer adverse effects.

        Lipid profiles including cholesterol and LDL are widely tested at GP surgeries, so this information is often available. It’s worth knowing what they are.

This is a dangerous time to let your cholesterol get too low.



          One in five people have metabolic syndrome and it has recently been found to treble the risk of dying from Covid and increase the risk of being hospitalised five-fold. And yet this is condition you can do a lot about.

         But what is metabolic syndrome?  It is also called insulin resistance and basically means the body has exhausted its ability to cope with sugar. It is one of the underlying mechanisms found in diseases such as diabetes, obesity, fatty liver and hypertension. See leaflet for further details. Routine blood screening will usually pick this up although my experience is many patients ae not always told they have metabolic syndrome. However, at the moment, this is something you would definitely want to know about.

         It is important because it is simple to treat. Stopping sugar and to a lesser extent refined carbohydrates is the key change you need to make (see leaflet for other measures). Doing this will also rapidly reduce the risk of Covid in anyone with metabolic syndrome and is not a bad idea anyway as sugar reduces immunity by up to 50%.

         Check if you have had a lipid profile, check if your triglycerides are high and your HDL low (see leaflet). These can be found along with cholesterol on the lipid profile. They are markers for metabolic syndrome as is an expanded waistline.


We hear a lot about Covid . We hear very little about prevention. But this blog is all about prevention. It is  about boosting immunity. And it’s not difficult to do.


  1. Garg H, Khanna P. Covid and cholesterol (C&C): Something to worry about and much ado about nothing?

doi:10.1016/j.tacc2020.09.03 (epub ahead of print)