Rules and Exceptions

Please review the rules and exceptions before going on to the more detailed entries. If you have questions after reviewing this section, please leave a note.


Review of general punctuation guidelines for use with numbers.

Use a period to separate a whole number from its decimal fraction.
After a number when using a numbered list.

Use commas to separate groups of 3 numbers in numbers of 5 digits or more unless decimals are used. The comma in a 4-digit number may be omitted.



NOTE: The AMA Manual of Style recommends compliance with SI conventions, separating with a "thin space," rather than a comma. This pertains to formal publications and scientific journals, rather than medical records documents. If you are typing/transcribing formal publications/journals, please refer to the AMA Manual of Style for details.

Use commas to separate unrelated numbers if neither can be expressed in words and the sentence cannot easily be reworded.


In the study sample of 1200, 690 were men.

However, if the sentence can be reworded or the number can be spelled out, spell out one number in order to avoid confusion.


In the study sample of 1200, six hundred ninety were men.
We used two 8-inch drains.

Use commas to separate the day of the month from the year when the full date is given. (see Dates entry)
Use commas to separate the year from the rest of the month when the full date occurs midsentence. (see Dates entry)

Use a comma to separate the chromosome number and sex chromosome in genetic expression. See also Genetics and chromosome punctuation.


46,XX (46 chromosomes, 2 each of chromosomes 1-22 and 2 X chromosomes in human female karyotype)
46,XY (46 chromosomes, 2 each of chromosomes 1-22 and 1 X and 1 Y chromosome in human male karyotype)
45,X (45 chromosomes, 1 X chromosome, Turner syndrome)

Use a comma to separate values of a single panel or test when writing laboratory values.


During the admission course, sodium was 136, 137, 142 and 140.

Do not use commas with numeric values in the following instances

Between words expressing a number


One million seven hundred sixty dollars was raised.

When only the month and a year are given


He was last seen in January 2007.
In June 2006, she was seen by the specialist.

Use a colon in standard expressions of time (see Clock time).

Use a colon in place of the word to in ratios.

Do not use a colon when writing military time.


Do not use hyphens with numbers:

To form a compound modifier between a number and a metric unit.


We made a 10 cm incision.

NOTE: This is a change from prior style. Compound modifiers should be formed by at least one complete word and metric values are not formed with complete words, but are abbreviated.

Do not use a hyphen when the number is the second part of the compound expression.

Please refer also to Classifications for specific information about numbers in scores and classification systems.

End of line wrap

Do not allow line wrap to separate a numeral from any relevant accompanying abbreviation or unit of measure. Use the forced space in your word processing program to keep these values together on the same line. (Consult the help file for the program if you don't know how to do this.)


Correct: The specimen was removed and measured
3 cm in diameter.

Incorrect: The specimen was removed and measured 3
cm in diameter.

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Page last modified on Sunday 11 of September, 2011 13:59:37 UTC by admin.
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