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How to Calculate When I Should Take a Pregnancy Test

author image Jennifer S. Wright
Since 2008, Jennifer S. Wright has written articles on a variety of topics including parenting concerns, medical conditions and nursing issues. Her articles have appeared in "LPN" magazine as well as on various online publications. An LVN since graduating from Weatherford College in 2005, Wright has taken care of elderly, pediatric and obstetric patients in hospital and home health care settings.
How to Calculate When I Should Take a Pregnancy Test
Don't take the test too early. Photo Credit: Izdebska/iStock/Getty Images

According to the National Institutes of Health, pregnancy tests performed at home are about 98 percent accurate when used properly according to the package directions. Pregnancy tests detect a hormone called HCG, for human chorionic gonadotropin, which is also referred to as the pregnancy hormone. This hormone is released when an egg implants into the uterus. The best time to take one of these tests is after you have missed a period. If you test too early, the amount of HCG in your urine may be too low for the test to detect.

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Step 1

Determine the first day of you last normal menstrual period. Mark this date with an X on a calendar.

Step 2

Add the number of days you usually have in a normal menstrual cycle to the date marked with an X and circle this new date. A menstrual cycle is counted from the first day of your period to the day before the first day of your next period. According to The National Women’s Health Information Center, an average menstrual cycle is 28 days long, but can range from 21 to 35 days in women and as long as 45 days in young teens. If you are unsure of the length of your menstrual cycle, add 28 days to the date marked with an X and circle the calculated date.

Step 3

Wait one day after the circled date and then take a pregnancy test, if your period has not yet arrived. You can test at any time of day, but your first morning urine has the highest concentration of the pregnancy hormone. Continue to the next step if the test is negative, but you still feel you might be pregnant or you are experiencing symptoms of pregnancy including tender breasts, nausea, vomiting, food aversions or cravings, dizziness, fatigue, headaches and mood swings.

Step 4

Wait one week from the date you took the first pregnancy test to take another test, if your period has not yet arrived. According to the Mayo Clinic, pregnancy tests claim accuracy as soon as the first day of a missed period, but waiting one week after a missed period will give you the most reliable results.

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