Hardly any vitamin gets as much hype – or sparks as much debate. Between “miracle cure for everything” and “totally overrated,” the sober truth about vitamin D sits in the middle: a real deficiency is genuinely common in Germany, especially in winter – but not every low number needs treatment, and more is definitely not better. Here's the honest picture: who should get tested, what the numbers mean, and when taking vitamin D is really worth it.
Key takeaways
- Your skin makes 80–90% of your vitamin D from sunlight – diet plays only a minor role.
- From October to March, the sun in Germany isn't strong enough for your body to make its own – you live off your summer reserves.
- A marked deficiency can contribute to bone and muscle pain, muscle weakness and more frequent infections.
- General screening isn't recommended – testing makes sense for people at risk and with matching symptoms.
- If you take it: dose it deliberately rather than experimenting with high doses – an overdose can harm you too.
What vitamin D can do – and what it can't
What's well established is its central role for bones and muscles: vitamin D regulates your calcium balance, and a marked deficiency leads to softening of the bones, muscle weakness, and a higher risk of falls and fractures in older age. Your immune system is involved, too. For many of the other promises – from preventing cancer to preventing depression by taking high doses when your level is already normal – the research is sobering. The honest formula: correcting a deficiency is worthwhile; pushing a normal level higher does nothing.
Possible signs of a marked deficiency
- Bone and muscle pain: often vague, typically in the back, pelvis and legs.
- Muscle weakness: climbing stairs feels hard, getting up from a chair feels unsteady – an important sign, especially in older people.
- More frequent infections: repeated respiratory infections can be linked to very low levels.
- Fatigue and low mood in winter: possible, but nonspecific – many causes compete here, from lack of daylight to your thyroid.
Who should get tested?
- People who rarely get any sun: mostly indoors, night shifts, clothing that covers the skin.
- Older people: aging skin makes far less vitamin D – while the risk of falls goes up.
- Darker skin types at our latitude: more pigment means slower production in the skin.
- People with chronic conditions: osteoporosis, chronic bowel, liver or kidney disease, and certain medications (e.g. cortisone, anti-seizure drugs).
Your numbers, briefly explained: The lab measures 25-OH vitamin D. Levels of 20 ng/ml (50 nmol/l) and above are usually considered sufficient; below that is the gray zone, and well below it is a true deficiency. Important: a slightly low winter level with no symptoms isn't a disease – and levels above 50–60 ng/ml bring no extra benefit, but can do harm.
