Persistent tiredness can leave you wondering what to discuss with a GP. This guide summarises NHS and NICE advice on assessment, tests that may be considered, when to seek help and how to prepare. It is written for adults in London who want to discuss a clear next step.
Short answer
NHS Tiredness and fatigue advises seeing a GP if tiredness lasts a few weeks without a clear reason or affects daily life. It says tests may check for anaemia, diabetes or hyperthyroidism. NICE CKS lists investigations to consider depending on clinical judgement, including full blood count and ferritin, inflammation markers, liver, kidney and thyroid tests, HbA1c and a coeliac screen. These are possible investigations, not a routine panel for everyone.
What a GP asks about first
NICE's guidance for assessing tiredness and fatigue in adults begins with questions, not tests. Expect to be asked about:
when it started, how severe it is, and what makes it better or worse, including rest, sleep and activity
daytime sleepiness, snoring or broken sleep, which can point to sleep apnoea or another sleep disorder
low mood, anxiety or stressful life events
other symptoms, such as weight change, palpitations, breathlessness or pain
diet, alcohol, smoking, medicines and supplements
your work pattern, including shifts and long hours
the chance of pregnancy, where relevant
Source: NICE Clinical Knowledge Summaries, "Tiredness/fatigue in adults: assessment" (last revised June 2025).
Which blood tests are usually considered
According to NICE CKS, a GP may consider the following, depending on clinical judgement. Not everyone needs every test.
Full blood count and serum ferritin: to look for anaemia and low iron stores.
ESR and CRP: markers that can be raised by infection or inflammation.
Liver function tests: to look for liver disease.
Kidney function and electrolytes: to look for kidney problems or a salt imbalance.
Thyroid function tests: to look for an underactive or overactive thyroid.
HbA1c: to check for diabetes.
IgA tissue transglutaminase: to screen for coeliac disease.
Calcium and phosphate: to check bone chemistry.
Urinalysis, and a pregnancy test where appropriate.
Source: NICE CKS, "Tiredness/fatigue in adults: assessment", investigations section. NICE also notes that further tests may be added depending on your symptoms.
Why "normal" results are still useful
A normal blood result does not explain every case of tiredness. NICE CKS warns that broad testing without supporting findings can give false positives and rarely helps diagnosis. NHS Tiredness and fatigue lists sleep problems, stress, hormonal changes, illnesses and medicines among possible causes. Discuss what results mean and what to do if symptoms continue.
Red flags: do not wait
Seek help according to your symptoms. The following NHS advice distinguishes a GP assessment from an emergency.
NHS Tiredness and fatigue advises seeing a GP for tiredness lasting a few weeks without a clear cause, tiredness affecting daily life, or tiredness with weight loss, mood changes or gasping, snorting or choking during sleep: https://www.nhs.uk/symptoms/tiredness-and-fatigue/
NHS When to call 999 says 999 is for life-threatening emergencies, such as strokes and heart attacks. If you are unsure whether to call 999, get help from NHS 111: https://www.nhs.uk/nhs-services/urgent-and-emergency-care-services/when-to-call-999/
Your pre-appointment checklist
NICE CKS suggests a symptom and sleep diary may help. Note symptom onset, medicines and supplements, diet, alcohol and work patterns for discussion. It does not prescribe a seven-day diary for everyone.
Free NHS routes, and when people choose private
You can contact your NHS GP surgery as well as considering private care. Compare the available appointment type and cost, and ask what any tests or follow-up would cost before choosing. A private appointment does not guarantee faster testing or a particular diagnosis.
Book a private GP appointment with The Online GP
Our fixed rate card is simple: a 15 minute phone consultation is £59, a video consultation is £150, and an in-person consultation is £220. Tell us on the call that you are tired and we will plan the right tests and next steps with you.
Call 020 3951 3429 to book.
Message us on WhatsApp: https://wa.me/447961280835
This article is general information and not a diagnosis. If you are worried about your health, speak to a doctor.
Written by The Wellness Team and medically reviewed by The Wellness Clinical Team.
Sources
NICE CKS, Tiredness/fatigue in adults: assessment. https://cks.nice.org.uk/topics/tiredness-fatigue-in-adults/diagnosis/assessment/
NHS, Tiredness and fatigue. https://www.nhs.uk/symptoms/tiredness-and-fatigue/