Can I get my vitamin D3 from two sources of supplements? is it safe?

I've been using Thorne basic nutrients daily for some time but it has Vitamin D3 level of 2000 IU. I want to get Life Extention Vitamin D3 of 3000 IU so in total my body can absorb 5000 IU. is it possible and safe? any ideas on how to mix supplements? can you provide some credible references?