Researchers haven't established a clear connection between menstrual cycles and blood sugar control, but some studies have shown a link. Here's a look at how and why your periods and your blood sugar may interact, whether you have type 1 or type 2 diabetes.

Your ovaries produce the hormones estrogen and progesterone, which regulate your menstrual, or reproductive, cycle. As the hormone levels fluctuate during the cycle, so can your blood sugar.

Your menstrual cycle has two phases: follicular and luteal. The follicular phase begins on the first day of bleeding. During the early part of this phase, estrogen and progesterone levels are low. The ovaries then begin gradually increasing production of estrogen as a result of the developing egg cell. At midcycle, around day 14, one of your ovaries releases an egg (ovulation).

The luteal cycle begins after ovulation and lasts about two weeks. During this time, the ovaries increase production of both estrogen and progesterone. The hormones prepare the lining of the uterus for implantation with a fertilized egg.

If the egg isn't fertilized, the ovaries stop producing estrogen and progesterone. That, in turn, causes menstruation, or the shedding of the blood and tissue that line the uterus. With that, another cycle begins.

What's the connection between these two hormones and blood sugar?

Estrogen may make your cells more receptive, or sensitive, to insulin. That is, more sugar leaves your bloodstream and enters individual cells, causing the level of sugar in your blood to drop.

Progesterone, on the other hand, may make your cells more resistant to insulin. That means more sugar stays in your bloodstream. The more progesterone released, the more resistant your cells are to insulin, so the more glucose stays in your blood, causing blood sugar levels to rise.

Production of these two hormones varies throughout the menstrual cycle and doesn't always occur simultaneously or to the same degree, so women may be affected differently. But in general, it's during those seven to 14 days before menstrual bleeding begins — during the luteal phase — that some women see fluctuations in their blood sugar levels despite maintaining stable doses of their diabetes medication. Blood sugar generally stabilizes a day or two after the period starts.

Blood sugar may also rise or fall because of another issue related to menstruation: premenstrual syndrome (PMS). Some women with PMS experience mood swings, irritability, bloating, lethargy and food cravings. And eating foods containing more carbohydrates and fats — common PMS cravings — also can affect blood sugar levels.

What you can do

When you have diabetes, controlling your blood sugar is one of the most important things you can do to prevent long-term complications, such as damage to your nerves, kidneys or eyes. Anticipating changes that menstruation may cause can help you manage your diabetes better and keep your blood sugar levels more stable.

Here's what you can do:

• Keep a log. Record your blood sugar levels each day — not just during menstruation. Also make note of any signs and symptoms you experience before menstruation, such as bloating, irritability, fatigue, cramps, weight gain or food cravings. Record the day your period begins and the day it ends.
• Review your logs. Review your logs to look for patterns in your blood sugar levels, especially around the time of your cycle.
• Consult your doctor. If you do notice menstruation-related changes, talk to your doctor about adjusting your treatment regimen. If you have type 1 diabetes (formerly called juvenile or insulin-dependent diabetes), your doctor may advise gradually increasing your insulin dose to coincide with expected increases in your blood sugar. Or if your blood sugar levels tend to drop around menstruation, your doctor may advise reducing your insulin dose. Perhaps all you need to do is adjust your meal or exercise program, or both, rather than alter medication dosages, particularly if you have type 2 diabetes (formerly called adult-onset or noninsulin-dependent diabetes).
• Follow normal diabetes management strategies. Sticking to your normal strategies to manage diabetes will help prevent wide blood sugar fluctuations during your menstrual period. Continue your normal meal plan and get regular physical activity, for instance, unless your doctor advises you otherwise.

There's also a flip side to the menstruation-diabetes connection. Diabetes can affect menstruation. Women who developed type 1 diabetes as children may experience abnormalities in menstruation. They may have longer cycles, menstruate longer and have heavier bleeding, for example. However, those problems often diminish as women approach the end of their reproductive years. In addition, polycystic ovary syndrome, a common problem in which ovulation fails to occur, is strongly associated with insulin resistance and type 2 diabetes.