Which is safer-expressing large amounts in numbers alone or numbers and words together? Is 1 million or 1,000,000 less likely to cause an error?

Using a combination of numbers and words is safer, especially when entering doses in computer systems, on medication administration records, and on labels applied by the pharmacy. Although the words "million" and "thousand" have nearly the same number of characters as the corresponding numbers, they're less prone to confusion because the letters differ and are more easily distinguishable than a series of zeros.

To be safe, use numerals with whole words (50 thousand, 1 million) when expressing large numbers, and don't abbreviate "thousand" or "million" in any way.