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Menstruation and type 1 diabetes

If you have type 1 diabetes, menstrual cycles can affect your type 1 management. Your blood glucose may rise higher than usual and you may be more resistant to insulin during your period. Everybody is different, so you may not notice a significant difference at all. Read on for information and advice to help you find what is normal for you.
Content last reviewed and updated: 09.08.2023

A woman who is laying on her bed, experiencing period pain as part of menstruation

How do periods affect type 1 diabetes?

Before and during your period, your body may respond differently to insulin. You may experience high and low blood glucose levels before and during your period.

If you can work out what pattern your body follows in the run up to and during your period, this will help you to manage these changes.

The important thing to note is that menstrual cycles are very different for everyone. There is no one size fits all.

How do periods affect insulin?

Your hormonal cycle – when oestrogen and progesterone levels rise and fall – is broken up into two phases: a follicular phase and a luteal phase.

During the luteal phase (10-14 days before a period), progesterone levels are higher which can cause insulin resistance for some people.

When progesterone levels are higher, this can trigger cravings for things like chocolate, sugary foods, and white bread. It can cause tiredness too, making it harder to exercise, which also increases insulin resistance.

Once you enter the follicular phase and your period starts, your insulin can suddenly seem like super-strength insulin. So you can go from high to low blood glucose levels which can be challenging. You may experience mood swings, feel down or irritable, and very tired.

How do periods affect blood glucose levels?

During the lead-up to a period, blood glucose levels tend to run higher than normal. During a period, glucose levels can be lower than normal. But for some people it can be the opposite. Others don’t notice an effect at all. And for some, it can change from month to month.

Checking blood sugar levels more frequently before, during and just after a period can help you to work out what your pattern is during your menstrual cycle. Technology, such as continuous glucose monitors (CGM) and flash glucose monitoring, is really useful in helping you make informed decisions about adjusting your insulin and the carbohydrate you’re eating to try and minimise the chances of hypos.

Can insulin affect your period?

Insulin itself doesn’t have a direct impact on your period.

Can type 1 cause heavy periods?

If you spend 70% or more in the optimal glucose range (usually 4-10 mmol/l), you may have a more stable menstrual period pattern (you can find out your time in range percentage on your CGM or flash glucose monitor). Genetics also have an influence, so what is ‘normal’ for one person with a 70% time in range will be different from others.

Spending a lot of time outside your target range probably means that there will be changes from month to month (depending on your cycle) and this could include heavier or missed periods. This is because extreme changes in glucose levels impact how your hormones work.

Some months, you may experience heavy bleeding, other months your cycle may be lighter. The heavier your cycle, the higher your insulin needs may be.

Can type 1 cause periods to stop or become irregular?

When you have type 1, you may experience irregular or unpredictable menstrual cycles. Keeping your glucose levels in target range 70% of the time will mean there is less impact on the hormones regulating your menstrual cycle.

It isn’t always possible to keep your blood sugars consistent. Things like stress or illness can make it harder to manage your blood glucose. These normal life events can cause your usual menstrual pattern to change.

If your periods stop for no reason, take a pregnancy test to rule out that possibility. Contact your GP in case you need a gynaecology referral.

Talk to your Diabetes Healthcare Team if you aren’t having periods at predictable intervals or need support to manage your blood glucose.

Make the most of technology

Keeping a menstrual diary alongside your blood glucose data will help you work out your pattern. Flash glucose monitors and continuous glucose monitors (CGMs) allow you to take notes so that you can look back over the logbooks and match your blood glucose data against your period.

Because it’s constantly recording, a glucose monitoring system makes it much easier to see what’s going on in terms of how your insulin is working and what your glucose levels are doing. It might help you to know for example whether you’re particularly insulin-resistant a few days before you’re due to start your period

What about DKA and the menstrual cycle?

If you become very insulin-resistant in the lead-up to a period and if your insulin dose is not adjusted, you may not have enough insulin in your system to break down carbs effectively to use as energy.

This can lead to a higher blood glucose level and may cause ketones build up in the body. Ketones build up when there is not enough insulin in the body to convert glucose to energy, so your body starts breaking down fat instead. Too many ketones can lead to diabetic ketoacidosis (DKA), which can be life-threatening if it is not treated quickly. It can also have an effect on ovulation and fertility.

If you are concerned about ketones, you can monitor your ketone level using a blood ketone monitor.

Technology like continuous glucose monitors or flash glucose monitors can help to monitor your blood sugar levels. Talk to your Diabetes Healthcare Team about the different options that are available and adjusting your insulin dose.

Can diet and exercise help with period symptoms?

Good nutrition, exercise, and regular sleep are good things for everyone, whether you have type 1 diabetes or not. Hormonal changes can make you feel hungrier which why you may have cravings for sugary food before your period.

Eating healthier carbs where possible may help to keep blood glucose levels more stable. If you’re able to exercise, finding a type of exercise that works for you may help with managing period symptoms.

Get support

Talk to your support network, and in particular family members who menstruate to get an idea of what their menstrual cycle is like. Connecting with other people who live with type 1 through online communities and forums can also be helpful.

Share any concerns about managing your blood glucose alongside your periods with your Diabetes Healthcare Team or you GP. You could also ask about options for controlling the hormonal shifts that happen during the menstrual cycle.

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