I was reading an older book I found and it was about vitamins and indicated to never take vitamin D without calcium as a warning. I'm wondering, because I only take vitamin D3 by itself, but I do take a multivitamin in the morning that does have some calcium.

The multivitamin has about 66mg of vitamin C that I take in morning and I take 2,000 ui in total for vitamin D3. 1,000 in the morning and 1,000 at night.

Personally I don't think it is usually necessary to take calcium at all.

The food sources of calcium are pretty readily available. Dairy, veggies, seeds/nuts and hard water, there is plenty of evidence food sourced calcium is used better than supplemental. I think it's probably counterproductive to take more than 600mg calcium/d.

The point is that when you increase your vitamin d status above 40ng/ml you will probably quadruple you body's ability to absorb calcium therefore the need for supplemental calcium is superfluous and possibly leads to increased risk of kidney stones and stroke.

If there is any supplement that using Vitamin d does raise the requirement for that is MAGNESIUM.
Because of the quadrupling of calcium uptake given increased 25(OH)D this can and often does reveal magnesium deficiency.
calcium tenses nerves and magnesium relaxes them
Calcium excites neurones magnesium calms them
Increase vitamin d status therefore, because of the imbalance between calcium and magnesium may leave magnesium deficient people feeling tense and edgy and possibly with muscle cramps.
It's not the calcium it's not the vitamin d it's the lack of counterbalancing magnesium.
Dr Davis says
3) Magnesium--I generally advise supplementation with the well-absorbed forms, magnesium glycinate (400 mg twice per day) or magnesium malate (1200 mg twice per day). Because they are well-absorbed, they are least likely to lead to diarrhea (as magnesium oxide commonly does).

How does Magnesium Citrate fair as far as being well-absorbed?

I'm far from an expert, but I've been taking vitamin D3 around 2,000 IUs daily and magnesium, either malate or citrate. I stopped taking additional calcium, besides what's in my daily multi, due to concern with arterial blockage and stroke.

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It's often a form recommended for constipation that implies it's not as good as magnesium malate. It's the hydroscopic properties of the magnesium that remains unabsorbed that attracts water to the stool and gets things moving. That said the citrate part of magnesium citrate is useful as is the malate side of magnesium malate.
As taking magnesium THROUGH the day is better than taking higher amounts once daily it could be a smart move to use a different form each time so as not to put all your eggs in one basket.

Krispin swears by Albion Patent mineral chelates she also says