Vitamins for your immune system: which ones actually matter

What actually supports immunity

Your immune system needs sleep, physical activity, a healthy weight, no smoking, vaccination and a diet without gaps. Supplements only cover that last point: they fix a shortfall but don’t push immunity above normal.

In the UK and northern Europe, low vitamin D is the most common problem. The NHS notes that most people get enough from sunlight only between late March or early April and September. Vegetarians and people who rarely eat meat or seafood can also run low on zinc.

Find your option: immunity

Pick your situation to see which nutrient makes sense and at what dose

Your situation

Winter, little sun Little meat or fish A cold is starting I get ill often

What makes sense

Vitamin D3

In a UK or northern European winter, skin makes almost no vitamin D.

Dose: NHS: 10 mcg (400 IU) a day in autumn and winter; no more than 100 mcg

D3 on iHerb Read the guide

Where to start

• Vitamin D3: doses in IU and mcg, the upper limit, and whether you need K2.
• Zinc: forms, safe doses, lozenges for colds and the risk of copper deficiency.
• Vitamins to take in winter: what changes from autumn to spring, and vitamin D in a UK winter.
• Vitamin D from sunlight in the UK: a month-by-month calendar for your city.

If you’re an adult catching more than 4–6 colds a year, or infections hit you hard, book a GP appointment rather than trying to fix it with supplements on your own.

Vitamins for immunity: what works and what doesn’t

This is the evidence for the supplements people most often put in their basket “for immunity”.

Nutrient	Who it makes sense for	Dose	What’s known
Vitamin D3	everyone in autumn and winter	10 mcg (400 IU), NHS advice	slightly lower risk of respiratory infections
Zinc	if your diet is low in it	10–15 mg	a deficiency weakens immunity
Zinc lozenges	first day of a cold	per label, briefly	shortened colds in some trials
Vitamin C	people under heavy physical stress	200 mg or more; adults need 40 mg	barely reduces the chance of catching a cold
Probiotics	after antibiotics	per strain studied	effects depend on the strain
NAC	not for everyday immunity	only with a doctor’s advice	evidence is limited
Elderberry	colds and flu	per label, briefly	preliminary evidence; raw or unripe berries are toxic
Quercetin	not for everyday immunity	per label	little research in people
Reishi mushroom	not for self-treatment	per label	little research in people
Propolis	not if you’re allergic to bee products	per label	limited evidence; allergic reactions are possible
Children’s vitamins	babies and children under 5	as the NHS and your GP advise	vitamin D is the main one

Once a cold has started, the useful options shrink to a couple. Step through them:

A cold is starting: what makes sense

Five steps, from day one to "why do I get ill so often?". Tap a step

1Day one 2Vitamin C 3Elderberry 4Afterwards 5Often ill

Zinc acetate lozenges

In some trials, lozenges started within 24 hours shortened colds.

• Only while the cold lasts, usually no longer than 1–2 weeks
• How many a day: follow the pack

What helps more than any bottle

These habits do more for your defences than supplements:

• Sleep 7–9 hours a night.
• Stay physically active most days.
• Don’t smoke.
• Keep your vaccinations up to date, including the flu jab if you’re offered it.
• Eat a varied diet with enough protein, fruit and vegetables.

Bottom line: what to choose

Autumn and winter

Vitamin D3, 10–25 mcg

Daily, with food; no more than 100 mcg

D3 on iHerb

Little meat or seafood

Zinc 10–15 mg

Picolinate or bisglycinate

Zinc on iHerb

First day of a cold

Zinc acetate lozenges

For a few days

Lozenges on iHerb

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FAQ

Does vitamin C help with colds?

Taking vitamin C regularly barely reduces the chance of catching a cold in most people, though it may slightly shorten colds. The effect is larger in people under heavy physical stress. Reviews found that starting it once you’re already ill doesn’t help.

How much vitamin D should I take in winter in the UK?

The NHS advises everyone to consider 10 mcg (400 IU) a day in autumn and winter. Some groups, such as people who rarely go outside or cover most of their skin, should take it all year. Don’t take more than 100 mcg (4,000 IU) a day.

What should I give my child for immunity?

The NHS advises a daily vitamin D supplement for babies and young children. Ask your health visitor, GP or pharmacist about the dose and form. Children don’t need zinc or other supplements without a reason.