Is fatigue a common side effect of breast cancer treatment?

Fatigue is very common during breast cancer treatment and can continue after treatment ends, sometimes lasting months to years. ^[1] Many people experience a deep, persistent tiredness that doesn’t fully improve with rest and may affect daily activities. ^[2] Fatigue can start within weeks of treatments like radiation and may range from mild to severe. ^[3] Sleep problems after cancer can also contribute to feeling worn out for months or even years. ^[4]

What causes cancer-related fatigue?

• Treatment effects: Chemotherapy, radiation, and targeted therapies can directly lower energy and cause inflammation. ^[3]
• Poor sleep: Insomnia, fragmented sleep, or daytime napping can worsen fatigue. ^[4]
• Nutrition and hydration: Not eating or drinking enough reduces energy and recovery. ^[3]
• Emotional stress: Anxiety and low mood commonly follow diagnosis and treatment and can drain energy. ^[4]
• Travel and logistics: Frequent trips to appointments add physical and mental strain. ^[3]

How to manage fatigue

Good news: fatigue can usually be eased with practical steps and support from your care team. ^[1]

Move your body regularly

• Aim for light-to-moderate activity such as walking, cycling, or gentle resistance training; these help lower fatigue and improve function. ^[5]
• Even short, regular sessions are beneficial; supervised programs may have stronger short‑term effects, but home‑based exercise also helps. [PM14]
• Combined aerobic and strength exercise tends to show the largest improvements in fatigue. [PM18]

Support better sleep

• Keep a consistent sleep schedule and limit long daytime naps to 15–20 minutes to protect nighttime sleep. ^[6]
• Practice wind‑down routines and manage night‑time awakenings to improve sleep quality and energy. ^[4]

Pace and prioritize

• Balance activity with planned rest breaks to avoid boom‑and‑bust cycles. ^[6]
• Ask for help with chores, and spread tasks across the week to conserve energy. ^[7]

Nutrition and hydration

• Eat small, frequent meals with protein, whole grains, fruits, and vegetables to stabilize energy. ^[3]
• Stay hydrated throughout the day, especially around exercise. ^[3]

Integrative approaches

• Mind‑body practices such as yoga, tai chi, qigong, cognitive behavioral therapy, massage, and acupuncture may reduce fatigue for some people. ^[8]
• Discuss any supplements with your clinician before starting, as benefits vary and interactions are possible. ^[7]

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Practical weekly exercise guide

Below is a general framework you can tailor with your clinician:

Goal area	Beginner target	Build-up target	Notes
Aerobic activity	10–20 minutes, 3 days/week	30–45 minutes, 3–5 days/week	Walk, cycle, or swim at a pace that allows conversation. [PM18]
Strength training	1–2 sets, 6–10 reps, 2 days/week	2–3 sets, 8–12 reps, 2–3 days/week	Use bands or light weights; focus on major muscle groups. [PM18]
Combined total	~90 minutes/week	≥180 minutes/week	Combined aerobic + strength shows greater fatigue reduction. [PM18]
Flexibility/balance	5–10 minutes after sessions	10–15 minutes after sessions	Gentle stretching, balance drills; consider yoga or tai chi. [8]

Start low and go slow; consistency beats intensity, and small gains add up. ^[5]

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When to contact your care team

• Sudden or worsening fatigue, dizziness, shortness of breath, chest pain, or palpitations. ^[3]
• Signs of depression or severe sleep problems that don’t improve with self‑care. ^[4]
• Considering new supplements or major changes in activity get personalized guidance first. ^[7]

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Key takeaways

• Fatigue is common during and after breast cancer treatment and can persist for months to years. ^{[1] [4]}
• Regular, gentle exercise especially combined aerobic and strength training reduces fatigue. ^[5] [PM18]
• Sleep hygiene, pacing, nutrition, hydration, and mind‑body therapies can meaningfully help. ^{[4] [6] [8]}
• Partner with your care team to personalize a safe plan and review any red flags. ^[7]