Workers in the commercial fleet sector are being advised to look out for signs colleagues might be addicted to drugs or alcohol.

According to the Department for Transport, drugs and alcohol cost British businesses more than £6 billion per year in lost productivity, while the Office for National Statistics reports that the number of deaths from drug and alcohol abuse has continued to increase over the last decade.

Suzannah Robin, an alcohol and drug safety expert for testing firm AlcoDigital, has listed five signs to look out for, which could suggest a co-worker is suffering from addiction.

She said: “Many organisations have now put in place policies to test staff for drugs and alcohol.

“However, while having a procedure in place will help to identify issues, employers should also be actively encouraging employees to come forward, and offering assistance and access to treatment for staff who are struggling.”

The list of warning signs is as follows:

1. Erratic behaviour and unpredictable mood swings – an individual may be happy and full of energy one minute, and then lethargic, depressed and irritable the next. He or she may also lose interest in activities and hobbies they’ve previously enjoyed, or become socially withdrawn and isolated.

2. Poor timekeeping and absenteeism – consistently turning up to work late and constantly taking time off could both be signs that something is wrong, particularly if there is a pattern for such occurrences taking place following the weekend or a stretch of annual leave.

3. Work-related performance issues – an inability to carry out basic tasks efficiently or effectively and an overall deterioration in the quality and quantity of work being completed.

4. Personal hygiene – neglecting cleanliness and grooming. Turning up looking dishevelled and unkempt.

5. Injuries and other physical changes – unexplained injuries, shaking, incoherent speech, bloodshot eyes and frequent nosebleeds are all possible signs a person may be abusing drugs or alcohol.

People who suspect a co-worker is suffering from substance abuse are advised to encourage them to seek professional help via their GP, a local treatment service or support group.