How hormones affect your energy levels

This kind of hormonal fatigue is more common than most people realise. These chemical messengers influence your metabolism, sleep, mood, and stress response in ways that directly affect how energised you feel.

A blood test is often the most direct way to understand whether a hormonal cause is driving your fatigue.

Thriva uses a short quiz to help you build a personalised at-home test. Try it now.

How thyroid hormones affect energy

Your thyroid produces hormones that regulate your metabolism, the process by which your body converts food into usable energy. When this goes wrong in either direction, you can feel fatigued.

With an underactive thyroid (hypothyroidism), your body’s processes slow down. You might feel persistently tired, gain weight, notice memory problems, or feel low in mood. With an overactive thyroid (hyperthyroidism), the opposite applies: restlessness, anxiety, and difficulty switching off are common, and disrupted sleep depletes your energy over time.

How oestrogen affects energy

Yes, low oestrogen can make you tired. Oestrogen supports many of the body’s processes, including the menstrual cycle, bone density, and metabolic function. Because oestrogen levels shift across the life cycle, dips in oestrogen produce noticeable dips in energy, and this is most pronounced during perimenopause and menopause.

The most common causes of low oestrogen include:

• Perimenopause and menopause: Oestrogen levels naturally fall as you approach menopause.
• Overtraining: High training volumes without adequate energy intake can suppress oestrogen production.
• Insufficient energy intake: Not eating enough to meet your body’s needs can disrupt hormone production more broadly.
• Certain medical conditions: For example, Turner syndrome.

Oestrogen and your menstrual cycle

During the follicular phase and around ovulation, rising oestrogen is associated with improved energy, better mood, and enhanced aerobic capacity. In the luteal phase (roughly week three) oestrogen falls, and many people notice a corresponding dip in energy and motivation.

Oestrogen, perimenopause, and menopause

As oestrogen declines through perimenopause, hormonal fatigue is a common experience. Mood changes, headaches, and difficulty concentrating often accompany this transition.

A 2020 systematic review found that higher endogenous oestrogen is associated with better sleep quality in premenopausal women, which may partly explain why energy so often dips as oestrogen falls.

Hormone replacement therapy (HRT) can restore oestrogen levels and may improve related fatigue and sleep symptoms. It’s worth discussing with your doctor if you’re in perimenopause or menopause and fatigue is significantly affecting your quality of life.

How progesterone affects energy

Yes, progesterone can make you feel tired or sleepy, and there’s a clear biological reason for it. Research suggests progesterone acts on GABA receptors in the brain—the same pathway targeted by many sleep medications—promoting relaxation and the onset of sleep. This is why fatigue is so closely tied to progesterone shifts across the menstrual cycle and at menopause.

Does progesterone make you tired or sleepy?

Progesterone peaks in week three of your cycle, which can cause daytime sleepiness, but may also mean deeper, more restorative sleep. In week four, as progesterone falls, sleep often becomes more disrupted, leading to tiredness and low energy in the run-up to your period.

So it can make you sleepy when it’s high and disturb your sleep when it’s low. Both outcomes end up affecting energy.

Progesterone and menopause

As you approach menopause, progesterone levels also naturally decline. This contributes to the sleep disturbances that are frequently reported during perimenopause, which in turn affects energy.

Find out more about your hormone levels with a Thriva test.

How testosterone affects energy

Testosterone is often described as a “male” hormone, but women produce it too, in smaller amounts, and it plays a meaningful role in energy, metabolism, and mood. Low testosterone in women has been associated with persistent fatigue and a reduced sense of wellbeing.

Testosterone levels naturally decline with age. In women, they can also be affected by oral contraceptives or conditions that affect ovarian function.

How cortisol affects energy

Cortisol is your primary stress hormone, designed to help your body respond to short-term pressure. Brief spikes in cortisol are a normal part of daily life, it can become a problem.

When stress is ongoing, your body can stay in a state of heightened alert for extended periods. Over time, chronically raised cortisol is associated with poor concentration, disrupted sleep, low mood, and weight gain, all of which compound fatigue. This pathway runs through the brain’s hypothalamic-pituitary-adrenal (HPA) axis, which regulates both the stress response and many aspects of energy balance.

While there’s no direct at-home test for cortisol, markers of chronic stress such as inflammation (CRP) and blood sugar (HbA1c) can be measured. Thriva uses a short quiz to help you build a test that can include both.

Other factors that can affect your energy levels

If hormones aren’t the primary cause, several other conditions commonly contribute to persistent tiredness:

• Iron deficiency anaemia: One of the most common causes of fatigue, particularly in women.
• Vitamin D deficiency: Low vitamin D is linked to fatigue, especially in the UK during autumn and winter.
• Too little exercise: Counterintuitively, physical inactivity tends to lower energy over time.
• Anxiety and depression: Mental health and energy levels are closely connected.
• Poorly controlled blood sugar: Whether through diabetes or insulin resistance, blood sugar dysregulation significantly affects energy.
• PCOS: Polycystic ovary syndrome affects hormonal balance and is a common cause of fatigue in women of reproductive age, often in combination with insulin resistance.

How to improve your energy levels

Finding the cause is the starting point. If you haven’t already, checking your thyroid function, iron, and vitamin D is a sensible first step. These are among the most common and most treatable drivers of fatigue.

Eat regular meals

Keeping blood sugar stable throughout the day is one of the most practical ways to maintain energy. Focusing on slow-releasing carbohydrates, protein, and fibre helps.

Some options worth trying:

• Porridge oats: A slow-release carbohydrate that supports steady energy and keeps you fuller for longer.
• Bananas: A convenient source of potassium, magnesium, fibre, and carbohydrates.
• Chia seeds: Their high fibre content slows digestion and supports energy stability.
• Black beans: A low-GI, high-protein food that helps stabilise blood sugar.

Stay active

Moving regularly supports energy levels, even when you’re already tired. According to NHS guidance on managing fatigue, even a brisk 15-minute walk can give your energy a meaningful boost.

UK guidelines recommend 150 minutes of moderate-intensity activity each week, or 75 minutes of vigorous activity. Moderate intensity means you can still hold a conversation. Vigorous means you can manage only a few words.

If you have any existing health conditions, speak to your doctor before significantly increasing your exercise intensity.

Manage your weight if needed

Carrying excess weight increases the body’s workload and can contribute to breathlessness and fatigue. If this is relevant to you, a doctor or registered dietitian can help you approach it safely and sustainably.

Takeaway

Persistent tiredness often has a hormonal component: thyroid function, oestrogen, progesterone, testosterone, and cortisol all affect energy in different ways. A blood test is often the most direct way to identify whether something measurable is driving how you feel.