Why High-dose vitamin C cause kidney stones ?

There are four main types of kidney stones:

1) Calcium-containing stones – these make up a majority, nearly 75% of stones (one related to Vitamin C)
2) Uric acid stones – these make up about 10% of stones.
3) Struvite (infected) stones – these make up about 10% of stones and form after an infection in the urinary tract.
4) Cystine stones – these are stones that form from the amino acid cystine, the most uncommon.

We've focus on the one highlighted.

Oxalic acid is a naturally occurring substance that can bind with minerals. Oxalates can crystallize with calcium to form kidney stones. When someone has lots of oxalates in their urine, it's likely coming from oxalate-rich plant foods or taking in vitamin C supplements (ascorbic acid). Vitamin C supplements can be metabolized to oxalic acid once ingested.

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1) Taking Calcium supplement at night
2) Eating Spinach and taking Vitamin C supplement in the morning

Would above diet cause lots of oxalates in urine?
Do you have any suggestions?
Thank you very much for any suggestions (^v^)

Absolutely. Two things to consider:

1)   Calcium needs to be coupled with vitamin D4.
2)   If you're male, you don't need that much calcium