Tired all the time even in summer

Feeling low on energy during summer might seem odd - after all, the days are longer, the sun is shining, and life tends to feel more active. But if you’re constantly tired, sluggish, or struggling to get through the day, you’re not alone. It’s a common issue, even in the warmer months, and it’s often linked to things like nutrient deficiencies, disrupted routines, or not sleeping well in the heat.

In this article, we’ll look at why summer fatigue happens, how diet and lifestyle can play a part, and how at-home blood testing can help you understand what’s going on - so you can feel more energised and in control of your health.

Common reasons you still feel exhausted in summer

1. Low vitamin D - even with sunshine

Indoor jobs, diligent sunscreen use, darker skin tone, or simply living in a city can block the UVB rays your skin needs to make vitamin D. Low levels may cause fatigue, muscles weakness, aches and changes in your mood, including depression.

2. Iron shortfall

Iron carries oxygen around the body. Ferritin is the protein that stores iron, and low levels often indicate that your iron levels are low. Heavy periods, plant-based diets, pregnancy and gastrointestinal issues can all drain ferritin stores below the optimal 30 µg/L mark. Symptoms such as shortness of breath, fatigue, dizziness or paler skin can hint at low iron.

3. Vitamin B12 deficiency

B12 keeps nerves healthy and red blood cells forming. Vegans, vegetarians, and people with gut-absorption issues may run low. Symptoms include persistent tiredness, pins and needles, or difficulties concentrating including brain fog.

4. Dehydration and disrupted sleep

Hot nights, late barbecues, and more caffeine or prosecco than usual all chip away at deep sleep and fluid balance, leaving you sluggish by mid-morning.

5. Heat-driven habit changes

Skipping breakfast because it’s “too warm”, exercising less, or reaching for quick sugar hits can swing blood-glucose levels and trigger energy crashes.

Signs your body needs an energy boost

You struggle to get out of bed, even after eight hours’ sleep
Brain fog slows decision-making
Climbing a flight of stairs feels tougher than it used to
Hair sheds more than normal when brushing
You feel dizzy or light-headed on standing
Exercise recovery takes much longer than it did last year

If any of these ring true for several weeks, it’s worth checking the levels of some key vitamins and minerals rather than simply blaming a “busy life”.

Should you supplement in summer?

Even in warmer months, supplements can play a helpful role in keeping your energy levels steady - especially if your diet is limited or your lifestyle reduces sun exposure. While it's always best to start with food and sunlight where possible, some nutrients are harder to get enough of without extra help.

Vitamin D is one of the most common deficiencies in the UK. Many people work indoors, use sunscreen daily, or have skin types that need longer sun exposure to make enough. Public guidance recommends everyone consider a 10 microgram (400 IU) daily supplement between October and March, or year-round if you're often indoors, wear clothes that cover your skin, or have dark skin as you will struggle to make enough Vitamin D from sunlight

Iron supports oxygen transport and energy production. If your stores are low, you might feel worn out or short of breath. Red meat, lentils, and leafy greens help, but if diet alone isn’t enough, a short course of supplements may be advised by your pharmacist or GP.

Vitamin B12 is found in animal products like dairy, eggs, and meat, so vegans and vegetarians often need to supplement. Older adults and those with gut absorption issues may also benefit. Fortified foods or a low-dose supplement can support nerve health and energy.

Foods that fuel steady energy

What you eat plays a huge role in how energised you feel throughout the day. Choosing the right nutrients can support red blood cell production, balance blood sugar levels, and help you feel more energised from morning to night.

Iron heroes: lean beef, chicken thighs, lentils, chickpeas, pumpkin seeds, and spinach. Pair plant sources with a vitamin C food such as peppers or strawberries at the same meal to absorb more iron.
B12 boosters: eggs, low-fat cheese, milk, fortified cereals, and nutritional-yeast flakes.
Vitamin D backups: grilled salmon, sardines on toast, cow’s milk, and fortified breakfast cereals.
Slow-burn carbs: oats, quinoa, and brown rice stabilise blood glucose better than white bread or pastries.
Hydration helpers: water flavoured with citrus slices, iced herbal tea, or homemade electrolyte drinks keep temperature and focus in check.

Simple lifestyle changes to boost energy levels

Small changes to your daily routine can make a big difference in how energised you feel. These simple lifestyle habits are especially helpful during summer when sleep, hydration, and movement patterns can easily be thrown off track.

Power-down routine: leave phones outside the bedroom one hour before lights-out; blue light delays sleep hormones.
Cool-down sleep: keep the bedroom below 20 °C; switch thick duvets for cotton sheets.
Coffee curfew: stop caffeine after 2 pm to protect deep sleep.
Sun-light snack: step outside mid-morning for 10 minutes of daylight; it sets your body clock and boosts vitamin D.
Move at cooler times: dawn walks or sunset yoga lift circulation without heat stress.
Plan rest: for every late night out, schedule one early-to-bed evening to repay sleep debt.

The role of at-home testing

If you've been feeling unusually tired for weeks and can’t quite figure out why, an at-home test may help you get to the bottom of it. Rather than guessing, a simple finger-prick blood sample provides clear, reliable information on key energy-related nutrients such as vitamin D, ferritin, and vitamin B12. With these results in hand, you can make informed changes to your diet or routine, knowing exactly what your body needs.

MyHealthChecked's Vitamin D Rapid Test gives you a fast, convenient way to check your levels, with results in just 10 minutes from a simple finger-prick sample. It's especially helpful if you've been experiencing fatigue, muscle weakness, aches, or changes in your mood – and want quick answers.

MyHealthChecked's Energy Profile Blood Test looks at 18 important health markers that may be linked to low energy. This includes vitamin D, active B12, folate, ferritin, thyroid function, kidney and liver health, full blood count, and inflammation markers like C-reactive protein. It’s a great option if you want a full picture of what could be affecting your energy.

If you're mainly interested in your vitamin and mineral status, MyHealthChecked's Vitamins & Minerals Blood Profile Test focuses on five key nutrients - vitamin D, active B12, folate, ferritin, and CRP. It's ideal if you suspect your diet might be missing something or you want a simple check before making lifestyle changes.

The process is quick and easy. You order a kit online, which arrives in discreet packaging. Using the lancet provided, you collect a small sample of blood and post the sample using the prepaid envelope. A UKAS-accredited lab tests your sample, and your secure digital results arrive in 2 to 3 working days. You’ll also receive clear guidance from a UK-registered doctor, with suggestions for what to do next. If your results show any areas that need improvement, you can take action - from tweaking your diet to retesting in a few weeks to track progress.

At-home testing can give you clarity and confidence, helping you take back control of your energy and wellbeing - even in the middle of summer.

In summary

Bright days don’t guarantee bright energy levels. Low vitamin D, iron, or B12, plus late nights and dehydration, can leave you yawning through summer. Small tweaks such as eating iron-rich foods, stepping outside daily, hydrating, and protecting sleep often spark noticeable improvements. When tiredness lingers, MyHealthChecked's Energy Profile Blood Test or MyHealthChecked's Vitamins & Minerals Blood Profile Test can help highlight areas worth exploring further, giving you a clearer sense of what to focus on next.

Reviewed by Dr Dave Nichols

References

1. National Institute for Health and Care Excellence. Vitamin D: supplement use in specific population groups. Public Health guideline PH56. London: NICE; 2014. Available from: https://www.nice.org.uk/guidance/ph56

2. NHS. Vitamin D. NHS.uk. 2017. Available from: https://www.nhs.uk/conditions/vitamins-and-minerals/vitamin-d/

3. National Institute for Health and Care Excellence. Vitamin B12 deficiency in over 16s: diagnosis and management. NICE guideline NG239. London: NICE; 2024. Available from: https://www.nice.org.uk/guidance/ng239

4. Kumar A, Marley A, Sharma E, Samaan MA, Brookes MJ, et al. Iron deficiency anaemia: pathophysiology, assessment, practical management. BMJ Open Gastroenterol. 2022 Jan; 9(1):e000759. doi:10.1136/bmjgast-2021-000759. Available from: https://bmjopengastro.bmj.com/content/9/1/e000759

5. GPnotebook. Tired all the time (TATT). London: Oxbridge Solutions Ltd; 2025. Available from: https://gpnotebook.com/pages/general-practice/tired-all-the-time-tatt