Look at your contract of employment to see whether there any specific requirements, such as attending a medical exam, for receiving and continuing to receive sick pay.

The written statement of particulars, which should be given to employees within two months of starting work, must specify the terms relating to sick pay, or refer to an easily accessible document which sets out those terms.

Usually the employer will ask employees to notify the employer early on the first day of absence. Often it allows self-certification for the first few days, before requiring medical evidence in the form of a 'fit note' from a GP.

For long-term sickness, or frequent short-term absences, the employer may, with your consent, seek a medical opinion from your GP or an occupational health (OH) specialist.

It is sensible to cooperate with your employer’s reasonable attempts to get expert advice about your medical condition. Otherwise, you risk your employer making decisions about sick pay and about your future employment without the benefit of medical input.

There is also the government's Fit for Work service, launched in December 2014. The service promises expert health advice to employers and workers via its website and telephone helpline, as well as a referral to an occupational health professional for all employees off sick or likely to be off sick for four weeks or more. Most referrals are via your GP.

Patients will not be referred to the new service if they are already fit to go back to work or if an on-going medical condition makes it obvious that the patient is likely to be off work for a considerable time.

The occupational health assessment is nearly always over the phone, with a follow-up face-to-face appointment if the occupational health professional thinks this is needed.

All referrals are voluntary and must be based on a worker's informed consent, which can be withdrawn at any time.

The occupational health professional can draw up a 'Return to work' plan, with recommendations to help the worker get back to work, and information on accessing appropriate services to help achieve this. No report or plan should be sent to the GP or employer without it first having been discussed with the worker, who can ask for changes, or refuse to agree to it being shared.

Return to work plans don't replace Fit Notes, but can be used as an alternative to the Fit Note.

If you are union member and you are concerned about a referral, contact your union rep.