Why am I always tired? The short answer
If you keep asking yourself “why am I always tired?”, the most common causes are ordinary and easy to check: too little or poor-quality sleep, sleep apnoea, lack of physical activity, stress, an unbalanced diet, or low iron or vitamin B12. Less often: thyroid problems, blood sugar, alcohol, medication or depression. If it lasts more than four weeks, see a doctor.
The reassuring part: most of the time, the doctor finds no serious illness. Here is how to narrow things down, when to see a doctor, and what NAD+ and vitamin B3 bring to the picture.
Key points
- In general practice, a serious physical illness is found in only about 4% of people who see their doctor for tiredness; depression in 18.5% (review of 26 studies).
- Adults need at least 7 hours of sleep a night, on a regular basis.
- Tiredness lasting more than 4 weeks, or accompanied by weight loss, fever or breathlessness, warrants medical advice.
- Nicotinamide riboside (NR), a form of vitamin B3, raises blood NAD+ in clinical trials; niacin contributes to the reduction of tiredness and fatigue.
What are the most common causes of persistent tiredness?
A review of 26 studies in general practice gives some benchmarks: anaemia in 2.8% of tired patients, serious physical illness in 4.3%, cancer in 0.6%, depression in 18.5% [1]. Most of the time, the cause lies in lifestyle or mood.
Too little or poor-quality sleep
This is the number one cause. The American sleep medicine societies recommend at least 7 hours a night, on a regular basis [2]. Quality matters too: irregular hours, late-night screens, a bedroom that is too warm, late coffee. See our article on disrupted sleep.
Sleep apnoea, often overlooked
Breathing stops several times an hour, causing brief awakenings. One global estimate puts the number of adults aged 30 to 69 affected at 936 million, 425 million of them with moderate to severe forms [3]. Typical signs: loud snoring, breathing pauses noticed by a partner, waking with a dry mouth, daytime sleepiness. Only a sleep study can confirm it.
Lack of physical activity
The paradox: the less you move, the more tired you feel. A meta-analysis shows that regular exercise increases feelings of energy and reduces fatigue, with a modest effect on average [4].
Stress and mental load
Ongoing stress makes sleep lighter, fuels rumination and leaves you with a “full head” in the evening. Our article on cortisol, the stress hormone, explains more.
Diet, iron, vitamin B12 and vitamin D
An unbalanced diet weighs on your energy, and iron matters particularly for women with heavy periods. In a trial conducted in France, 198 tired women who were not anaemic but had ferritin below 50µg/L received 80mg of iron a day or a placebo for 12 weeks: their fatigue score fell by 47.7% on iron, compared with 28.8% on placebo [5]. But don't take iron blindly: too much is harmful, so get tested first.
Vitamin B12 deficiency mainly affects vegans, older people and some people on long-term medication. Vitamin D is often low in winter; your doctor can test it, but it has no official health claim related to tiredness.
Thyroid and blood sugar
An underactive thyroid can cause tiredness, feeling cold, weight gain and dry skin: a TSH blood test can check this. Poorly regulated blood sugar can show up as energy slumps after meals, unusual thirst or needing to urinate often. See our guide to insulin resistance.
Alcohol and medication
Alcohol helps you fall asleep, but it disrupts the second half of the night and delays REM sleep [6]: you sleep, but you recover less. Some medicines also cause tiredness (antihistamines, sleeping pills, anti-anxiety drugs, some antidepressants or beta blockers). Don't stop anything without medical advice.
Low mood or depression
Nearly one in five people who see their doctor for tiredness has depression [1]. Loss of interest, sadness or irritability almost every day for more than two weeks is a reason to talk to someone. It can be treated.
What kind of tiredness do you have? A table to narrow it down
When the tiredness appears gives you a clue; this table is a guide and does not replace medical advice.
| Time or type of tiredness | Common causes | What to do |
|---|---|---|
| On waking | Too short a night, irregular hours, alcohol in the evening, bedroom too warm, sleep apnoea | 7 hours or more at fixed times, no alcohol in the 3 hours before bed, mention any snoring to your doctor |
| After eating | Large meals, fast sugars, alcohol at lunch, poorly regulated blood sugar | Vegetables and protein, moderate portions, a 10-minute walk afterwards, a blood sugar test if you have thirst or repeated energy slumps |
| In the afternoon (2–4 pm) | Natural dip in the body clock, sleep debt, lack of water or daylight | A 10- to 20-minute nap before 3 pm, get out into daylight, drink water, take an active break |
| In the evening, “nervous” exhaustion | Stress, mental load, screens, no breaks | Regular short breaks, screens off in the evening, gentle activity |
| In winter | Less daylight, shifted body clock, less activity, low vitamin D, infections | 20 to 30 minutes outdoors in the morning, regular activity, a blood test if the tiredness persists |
| Despite plenty of sleep (9 hours or more) | Unrefreshing sleep (apnoea), depression, thyroid, anaemia, medication, recovery from illness | See a doctor: this is the pattern that most warrants a check-up |
How can you narrow it down yourself?
Keep a tiredness diary for two weeks. Each day, note your bedtime and wake-up time, your energy level (score out of 10) at 10 am, 2 pm and 6 pm, your meals, coffee and alcohol, your activity, your stress and, for women, the days of your period.
Then ask yourself: since when? Does the tiredness go away on holiday? Do you mainly feel sleepy, or do you lack energy even when rested? Any new medication? This diary will also save your doctor time.
When should you see a doctor, and what tests are usual?
See a doctor if the tiredness lasts more than four weeks with no explanation, or sooner if you notice any of these warning signs:
- unintentional weight loss;
- fever, night sweats;
- breathlessness, palpitations, chest pain;
- pallor, very heavy periods, blood in the stools;
- intense thirst, needing to urinate often;
- falling asleep without meaning to, especially at the wheel;
- lasting sadness, dark thoughts (in France, the 3114 suicide prevention line answers 24/7 if you are in distress).
After asking questions and examining you, the doctor may order a blood test: full blood count, ferritin, fasting blood glucose, TSH, CRP, sometimes vitamin B12 or vitamin D. If sleep apnoea is suspected, a sleep study may be offered. Testing for “everything” with no specific signs is rarely useful [1].
So where does cellular energy fit in?
NAD+, a cornerstone of the mitochondria
Mitochondria turn nutrients into ATP, the molecule that powers almost everything your body does. To do this, they need NAD+, a coenzyme that carries electrons. It is also essential for enzymes that repair DNA [7].
Levels that fall with age
NAD+ gradually declines with age in several tissues, in animals as in humans [7]. Our article on NAD+ and its decline covers this in detail.
The role of vitamin B3
The body makes NAD+ from vitamin B3: nicotinic acid, nicotinamide or nicotinamide riboside (see our comparison of the forms of vitamin B3). EU law authorises two claims that are relevant here: “Niacin contributes to the reduction of tiredness and fatigue.” and “Niacin contributes to normal energy-yielding metabolism.” [8].
What studies on nicotinamide riboside show
NR raises blood NAD+. A single 300mg dose, the amount in one capsule, is enough to raise NAD+ in blood cells [9]. At 300mg a day, blood NAD+ rose by 51% within 2 weeks in healthy adults [11]. Over six weeks, in adults aged 55 to 79, NR was also well tolerated [10].
In short: NR reliably raises blood NAD+. NR is a form of vitamin B3; niacin contributes to the reduction of tiredness and fatigue. It complements a healthy lifestyle: sleep, activity, diet.
Hexagon® NAD+ at a glance
- 300mg of nicotinamide riboside chloride (NR) per capsule, 1 capsule a day with a large glass of water.
- 30 capsules (1 month) €34.90 · 60 capsules (2 months) €59.90 · 90 capsules (3 months) €79.90 · 180 capsules (6 months) €129.00, subscription available.
- Vegan, no controversial additives.
In clinical trials, NR raises blood NAD+ levels. Code HEX10: −10% (one use per customer). Discover Hexagon® NAD+
What can you do, starting this week?
- A fixed wake-up time and at least 7 hours of sleep.
- A 20- to 30-minute walk in the morning daylight.
- No coffee after 2 pm, and no alcohol in the 3 hours before bed.
- A tiredness diary, and a doctor's appointment at the first warning sign.
- Normal test results and want to top up your vitamin B3 intake? Niacin contributes to normal energy-yielding metabolism.
Your daily vitamin B3
- Hexagon® NAD+: 300mg of NR per capsule, 1 capsule a day.
- From 30 capsules (1 month, €34.90) to 180 capsules (6 months, €129.00), subscription available.
- Vegan formula, no controversial additives.
In trials, NR consistently raises blood NAD+. NR is a form of vitamin B3; niacin contributes to normal energy-yielding metabolism. Code HEX10: −10% (one use per customer). Discover Hexagon® NAD+
Frequently asked questions
Why am I always tired and sleepy?
Tiredness is a lack of energy; sleepiness means dozing off easily in front of the TV, in meetings or in the car. Marked sleepiness points first to sleep (accumulated sleep debt, apnoea) and should be reported to a doctor, especially if you drive.
Why am I tired when I'm not doing anything?
Precisely because inactivity is tiring: the body becomes deconditioned, sleep gets lighter, mood drops. Build back up gradually, adding a few minutes of walking each day.
I'm tired and I feel weak: what should I do?
Real muscle weakness (difficulty climbing stairs or raising your arms) is not just weariness: see a doctor promptly. Dizziness and pallor can suggest anaemia. Sudden weakness on one side of the body or sudden difficulty speaking means you must call 15 (the French emergency medical number; 112 anywhere in the EU).
Why am I so tired at the moment?
Look for what has changed: a recent viral infection (tiredness can linger for a few weeks), the clocks changing, a busy period, jet lag, a new medication. If it persists with no explanation, see a doctor.
Which vitamin should I take if I'm always tired?
Several nutrients carry the official claim “contributes to the reduction of tiredness and fatigue”: vitamins B2, B3, B5, B6, B9, B12, C, iron and magnesium. For example: “Vitamin B12 contributes to the reduction of tiredness and fatigue.” For iron, always get tested first.
How long should I take nicotinamide riboside before judging?
Blood NAD+ rises quickly: +51% after 2 weeks at 300mg a day, in an 8-week trial [11]. Take your capsule every day at the same time, and take stock after six to eight weeks with your tiredness diary.
Conclusion
Tiredness that won't go away almost always has a concrete explanation: sleep, activity, stress, diet or a deficiency that can be tested for. If you then want to top up your vitamin B3 intake, Hexagon® NAD+ provides NR, a form of vitamin B3 that raises blood NAD+ in trials, alongside good habits.
Sources
- Stadje R, et al. The differential diagnosis of tiredness: a systematic review. BMC Fam Pract. 2016;17:147. doi:10.1186/s12875-016-0545-5
- Watson NF, et al. Recommended Amount of Sleep for a Healthy Adult: A Joint Consensus Statement of the American Academy of Sleep Medicine and Sleep Research Society. Sleep. 2015;38(6):843-844. doi:10.5665/sleep.4716
- Benjafield AV, et al. Estimation of the global prevalence and burden of obstructive sleep apnoea: a literature-based analysis. Lancet Respir Med. 2019;7(8):687-698. doi:10.1016/S2213-2600(19)30198-5
- Puetz TW, O'Connor PJ, Dishman RK. Effects of chronic exercise on feelings of energy and fatigue: a quantitative synthesis. Psychol Bull. 2006;132(6):866-876. doi:10.1037/0033-2909.132.6.866
- Vaucher P, et al. Effect of iron supplementation on fatigue in nonanemic menstruating women with low ferritin: a randomized controlled trial. CMAJ. 2012;184(11):1247-1254. doi:10.1503/cmaj.110950
- Ebrahim IO, et al. Alcohol and sleep I: effects on normal sleep. Alcohol Clin Exp Res. 2013;37(4):539-549. doi:10.1111/acer.12006
- Covarrubias AJ, et al. NAD+ metabolism and its roles in cellular processes during ageing. Nat Rev Mol Cell Biol. 2021;22(2):119-141. doi:10.1038/s41580-020-00313-x
- Commission Regulation (EU) No 432/2012 of 16 May 2012 establishing a list of permitted health claims made on foods, other than those referring to the reduction of disease risk and to children's development and health. EUR-Lex
- Trammell SA, et al. Nicotinamide riboside is uniquely and orally bioavailable in mice and humans. Nat Commun. 2016;7:12948. doi:10.1038/ncomms12948
- Martens CR, et al. Chronic nicotinamide riboside supplementation is well-tolerated and elevates NAD+ in healthy middle-aged and older adults. Nat Commun. 2018;9:1286. doi:10.1038/s41467-018-03421-7
- Conze D, Brenner C, Kruger CL. Randomised, double-blind, placebo-controlled 8-week trial on the safety and metabolism of nicotinamide riboside chloride in healthy overweight adults. Sci Rep. 2019;9(1):9772. doi:10.1038/s41598-019-46120-z
Food supplements should not be used as a substitute for a varied and balanced diet and a healthy lifestyle. Ask a healthcare professional for advice if you are taking medication, pregnant or breastfeeding.
