Many women, particularly adolescent women, suffer from painful menstrual cramps, medically referred to as dysmenorrhea. Common treatments for menstrual cramps are non-steroidal anti-inflammatory drugs and oral contraceptives, but both have side effects that limit their use. Injection of vitamin K into an acupuncture point has been used as treatment for dysmenorrhea at the Obstetrics & Gynecology Hospital in Shanghai, China since at least 1985. More research is needed on the effectiveness of this treatment and its acceptability to different women. The objective of this study is to examine the feasibility and effectiveness of acupoint injection of vitamin K1 for the treatment of severe primary dysmenorrhea in the United States. Twenty participants will be randomized to receive either 1) vitamin K1 injection into an acupuncture point at the start of their menstrual cycle followed by a saline injection in a non-acupuncture point two months later or 2) saline injection in a non-acupuncture point followed by vitamin K1 injection into an acupuncture point two months later. The primary outcome measure will be change in pain intensity measured before and after each treatment. Data on other menstrual symptoms will be collected by telephone or a web-based survey. Three additional participants will be recruited to receive vitamin K1 injection into an acupuncture point and have blood samples drawn before and after injection to determine absorption of vitamin K1. The aims of the study are to collect preliminary data on the efficacy and safety of vitamin K1 injected in an acupoint for the treatment of severe primary dysmenorrhea; assess the feasibility and acceptability of the treatment among U.S. women; and test the blood absorption of vitamin K1 following acupoint injection treatment.

The investigators hypothesize that:

1. Vitamin K1 acupoint injection is a safe treatment for women with menstrual pain.
2. Vitamin K1 acupoint injection reduces menstrual pain more than placebo saline injection does.
3. The treatment of vitamin K1 acupoint injection is acceptable to U.S. women.
4. Vitamin K1 is absorbed into the blood thru acupoint injection.

Inclusion Criteria:

• Young women age 18-25
• Severe primary dysmenorrhea (defined as severe, recurrent painful periods for 6 months or more, that are not due to any other diagnosis, and that have not been relieved, or have been only partially relieved by any other treatment)
• Nulliparous
• English speaking
• No acute or chronic conditions diagnosed or suspected
• Not on hormonal contraceptives
• Regular menstrual cycles for at least 6 months
• Has a working phone or pager

Exclusion Criteria:

• Use of hormonal contraceptives, or intra-uterine device
• Pregnancy
• Dysmenorrhea due to any other suspected or recognized causes
• History of abdominal surgery
• Participation in other concomitant therapy for acute or chronic pain
• Current treatment with anti-coagulant drugs for any reason
• Previous treatment with vitamin K acupoint injection
• Plans to be out of area during next 5 months
• Under age 18
• Known allergy to Vitamin K.