Vitamin D: You're Passing Wrong Arguments Everyone knows about vitamin D. Almost nobody is calling it correctly.

Wrong Type
javascript
// ❌ What most people take
const vitaminD = "D2" // ergocalciferol
// cheap, synthetic, ~87% less effective at raising blood levels

// ✅ What you actually want
const vitaminD = "D3" // cholecalciferol
// what your skin produces naturally. use this.

If your bottle just says "Vitamin D" without specifying D3 — you're running D2. Check the label.

Missing Required Parameter
javascript
// ❌ Undefined behavior
vitaminD3.take({ withFood: false })
// fat-soluble vitamin + no dietary fat = poor absorption
// silent failure, no error thrown

// ✅ Correct call
vitaminD3.take({
withFood: true,
fatContent: "eggs | avocado | olive oil | nuts"
})

Vitamin D is fat-soluble. No fat in your digestive system when you take it means a significant portion never absorbs. This is not optional configuration.

Unhandled Side Effect
javascript
vitaminD3.take()
// side effect: increases calcium absorption
// WARNING: calcium requires routing or it deposits in wrong locations

// ❌ Missing dependency
import K2 from "supplements" // not installed

// ✅ Handle the side effect
import { D3, K2_MK7 } from "sunday-natural"
D3.take({ paired: K2_MK7, dose: "100mcg" })
// K2 MK-7 routes calcium to bones, away from arteries

D3 without K2 is an unhandled side effect. Most standalone vitamin D supplements ship without this dependency. Most developers wouldn't ship code with an unhandled side effect either.

Hardcoded Deprecated Value
javascript
// ❌ Legacy default — set in the 1970s for rickets prevention
const dailyDose = 400 // IU

// ✅ Dynamic — based on actual blood level data
const bloodLevel = await getBloodwork("25-hydroxyvitamin-d")
const dailyDose = calculateDose(bloodLevel, targetRange: "40-60 ng/mL")
// typical result: 2000–4000 IU for maintenance

The 400 IU default on most labels was never designed for optimization. It was designed to prevent deficiency disease in the 1970s. You're not in the 1970s. Get your levels tested and dose to actual data.

The Correct Implementation
D3 (2000–4000 IU) + K2 MK-7 (100mcg)
→ morning
→ with fat-containing meal
→ dose based on bloodwork, not label default

For a formula that ships with the correct defaults out of the box — sunday.co.ua carries Sunday Natural, direct from Germany. D3+K2 MK-7 combined, bioavailability-first formulation.

No configuration required.