Vitamin D3 — the SA dose, why blood levels matter
Despite SA's reputation as the sunshine country, indoor lifestyles, melanin and sunscreen mean most South Africans run vitamin D insufficient (25(OH)D < 75 nmol/L). The maintenance dose for adults is 1,000–4,000 IU of D3 (cholecalciferol) daily, ideally to a measured target of 75–150 nmol/L.
Why D3, not D2
D3 (cholecalciferol) raises and maintains serum 25(OH)D roughly 2× more effectively than D2 (ergocalciferol) (Tripkovic et al., 2012). All SA serious supplementation should use D3.
What dose for what level
| Goal | Daily dose | Expected serum 25(OH)D |
|---|---|---|
| Maintenance, sufficient | 1,000–2,000 IU | 75–100 nmol/L |
| Correction, mild insufficiency | 2,000–4,000 IU | 100–125 nmol/L |
| Deficiency (<50 nmol/L) | 5,000 IU under supervision | retest at 12 weeks |
Pair with K2 (MK-7)
Vitamin K2 directs the calcium that D3 helps you absorb to bone and away from soft tissue. A common stack is D3 5,000 IU + K2 (MK-7) 100 mcg daily.
Vitamin D3 FAQ
Can I just get D from sun?
Possibly — but SA epidemiology says most don't. Get a 25(OH)D blood test before assuming you're sufficient.
How much is too much?
The tolerable upper intake is 4,000 IU/day for adults. Higher doses under medical supervision are sometimes used for short-term correction.
When should I take it?
With a fatty meal — D3 is fat-soluble. Morning or evening is equally fine.
Does it interact with medication?
Speak to your doctor on certain anticonvulsants, steroids and weight-loss drugs that affect D3 absorption.
Is it safe in pregnancy?
Yes — sufficiency is recommended in pregnancy. Most prenatal guidelines target 1,000–2,000 IU daily.