Why Am I So Tired In The Autumn?

You might notice that as soon as summer ends and the evenings draw in, your energy levels start to dip. It isn’t your imagination, autumn tiredness is very real. There are several reasons behind it, from changes in daylight to shifts in routine and even nutrition. Understanding what’s going on inside your body is the first step to fixing it.

Less sunlight, less vitamin D

One of the most significant factors is the sharp reduction in daylight hours. In the UK, by late September, we lose around four minutes of daylight every day. Less exposure to sunlight means your body produces less Vitamin D, which plays a crucial role in energy, mood and immunity. ¹

Low Vitamin D has been linked with fatigue and even symptoms of seasonal affective disorder (SAD), a type of depression that appears in autumn and winter. ² Supplements are often recommended during these darker months to keep levels topped up.

Your body clock gets confused

Another reason for autumn fatigue is the disruption to your circadian rhythm, your internal body clock. Shorter days and longer nights can trick your brain into thinking it should be winding down, even when it’s mid-afternoon. That’s why you might feel sleepy earlier than usual.

Melatonin, the hormone that helps regulate sleep, increases with longer periods of darkness. ³ That can leave you feeling drowsy during the day and interfere with the quality of your sleep at night.

Temperature drops and energy use

Colder weather also plays a part. Your body uses more energy to keep warm as the temperature drops, which can leave you feeling drained. Combine that with the extra calories many people consume in autumn (comfort food season, anyone?) and you have a recipe for sluggishness.

Nutrition and lifestyle shifts

In summer, we naturally eat more fresh fruit and salads. Come autumn, heavy meals and less colourful plates tend to creep in. While there’s nothing wrong with a hearty stew, diets lower in fresh produce can reduce your intake of essential vitamins, minerals and antioxidants. These nutrients play a big role in fighting fatigue and supporting your immune system.

Add in less outdoor activity and more time indoors, and the tiredness can quickly build up.

Practical ways to beat autumn tiredness

The good news? You don’t have to resign yourself to three months of sluggishness. Small daily changes, backed by smart nutritional choices, can make a noticeable difference.

Get outside daily

Even if the sun isn’t shining, daylight exposure helps regulate your circadian rhythm. A 20–30 minute walk outside in the morning or early afternoon can help reset your body clock and improve energy.

Support with vitamin D

Since the NHS recommends everyone in the UK take Vitamin D during autumn and winter ⁴, this is one of the simplest and most effective steps you can take. A daily supplement supports not only energy but also your immune system, which often takes a hit in colder months.

Balance your plate

Try to keep your meals colourful. Vegetables, lean proteins, whole grains and healthy fats all contribute to energy metabolism. Leafy greens provide magnesium, which supports muscle and nerve function. Vitamin C-rich foods like peppers and citrus boost immunity while helping absorb iron, another energy-critical nutrient.

For extra gut health support, probiotics and fibre supplements such as psyllium husk can help keep digestion smooth and prevent sluggishness that stems from poor gut function.

Keep moving

It’s tempting to curl up on the sofa when the evenings get dark, but staying active is one of the best ways to fight fatigue. Exercise boosts endorphins, improves sleep quality and supports circulation. Even light activity like yoga or brisk walking can make a difference.

Prioritise sleep hygiene

Since darker evenings may already be triggering earlier melatonin release, stick to a consistent bedtime routine. Limit screens in the hour before bed, create a cool and dark sleep environment, and avoid caffeine after midday.

Supplements that can help

While lifestyle changes should always come first, supplements can provide valuable support during autumn.

Vitamin D: The most important for energy and immunity during darker months.
Vitamin B12: Essential for red blood cell formation and energy metabolism. Especially important for vegetarians and vegans.
Magnesium: Supports muscle relaxation, sleep quality and nervous system health.
Omega 3: Helps support mood, brain health and heart function.
Iron: If you’re feeling especially tired, iron deficiency may be a factor. Pairing iron-rich foods or supplements with Vitamin C helps absorption.

A comprehensive multivitamin can also cover multiple bases and ensure you’re not missing key nutrients when your diet shifts seasonally.

Autumn is a season of change, but that doesn’t mean you need to feel constantly tired. By understanding why seasonal fatigue happens, and taking steps to support your body with light, movement, nutrition and supplements, you can stay energised right through to winter.

Instead of surrendering to sluggishness, see autumn as an opportunity to reset your routine, nourish your body and build resilience for the colder months ahead.